No need to spend big bucks to get wifi internet in the van with a router and why roof mounted antennas and MiFis are a waste of time

EDIT 2024. I have been getting some stick online from various "experts" who are adamant that the only method worth considering is to have a roof mounted antenna, and various other gizmos, usually costing £300 or more in total. As I explain below, you simply don't need to go to this expense. The number one technical requirement to get a decent mobile signal is the size of the antenna. Once you have a big antenna, as found in a full size router, as opposed to the tiny antennas built into the body of a MiFi unit or a normal phone, you get 90% of the advantage. It is antenna size that is the major factor. Phone antennas are small simply because they have to be. Mifis are the same - any Mifi is a complete waste of time in a motorhome because size and portability and battery power are not a factor - Mifis are for travellers who stay in hotels. I will go further .... the Netgear Mifis, Nighthawk etc, are ridiculously overpriced, and are all easily outperformed by a "normal" 12v full size router such as the B525, placed by a window.

The reasons for the arguments are purely commercial. There is no profit in a secondhand fifty quid Chinese router - it is as simple as that. So companies such as Solwise and Motorhome WiFi dress it up as a technical subject and sell it to you as a package. Nothing wrong with that, good luck to them. But I am not involved commercially, I don't sell anything, I am a motorhome blogger with no axe to grind, and I just happen to have an interest in radio technology, having held an amateur radio licence for 30 years - and to get one of those you have to pass an exam, and 30 years ago it was quite a tough one - I even had to learn morse code.

The title of this blog says it all - there is simply NO NEED to spend over £300 for a router based motorhome wifi system. or to put it another way, the £50 option performs as well as the £300 option.

I now have a standing bet - a bottle of champagne - the proper stuff - for the van that parks next to mine and shows a working internet connection from the same network that is only available to him and not to me.

Here is the original blog .....

You don't need anything fancy to get the best chance of internet in the van over 4G. It's the size of the antenna that counts, not the location. The antennas in a proper full size router are 10 times bigger than the tiny antennas in a phone - that's why a router will pull in a signal long after the phone (hotspot) says no service.

The advantage of paying extra for a roof mounted antenna, plus the cables and adapters is negligible, and I have proved this by experimentation, based on my training in antenna theory as a licensed radio amateur. Antenna performance is like earthquakes - the scale of power is logarithmic. This means that for noticeable gains the performance has to double each time.

So the biggest gains are made by having a much bigger antenna. But after that, the positioning of the big antenna is less important, so the difference between on the roof, and just a meter or so below, by a window, or on the dash, is hardly noticeable.

EDIT see below about the insides of a roof MIMO antenna.

So all I use now is a Huawei B525 12v mobile router, which can be had for around £50. It lives on the front dash, or inside a cupboard if it is too sunny. The only time I have to try and reposition it is on the rare occasions I get no signal, or just 1 bar - in these situations it rarely improves. There has to be a minimum signal strength to support a decent data rate - so if there is no signal at all, then that's that.

In my early days of experimenting I used to put the router on the roof temporarily, in a plastic box. But I soon learned that no signal in the van (by a window) was no different to being on the roof.

If you are slightly technically minded, here is the methodology - the B525 has a page which displays signal strength and quality of signal parameters - QOS.

This a screen shot of the numbers with the router on its internal antenna by a window. With my roof top antenna the numbers were barely changed. The reason I did the experiment was that my rooftop antenna terminated in the wardrobe, so the router had to be there. But then I couldn't see the lights on the router, which was a pain. So I relocated the router inside the van where I can see it, and for the last few years have monitored it quite carefully - hardly any difference. I have never had a situation where I had no signal, and reconnecting to the roof antenna gave a signal. If there is no signal, there is no signal. 

The Huawei has proved very reliable and easy to use - when I change country and get a new sim, in it goes and 9 times out of 10 it connects immediately.

The takeaway for full timers is that you don't need to spend more than the cost of a Huawei B525 - about £50. There is a whole family of 12v mobile routers - others are available, but I like Huawei - mainly because of the software and firmware.

There is no point at all for the average motorhome owner to pay silly money for any of these expensive "motorhome wifi" kits. All you need is a 12v router costing around £50. There is also no need for any sort of power conditioning, as often suggested. They work fine on any voltage that can happen in a van - from 11v to over 14v. Now that I am on lithium batteries my resting voltage is 14.4v for days at a time (when plugged in) and I have not had a single failure of anything 12v in the van.

With regard to SIM cards - that is a big subject, as is EU roaming. In the UK I have found the EE network to be best, but EE is expensive. Three are the cheapest - you can get unlimited data on a 1 mont contract for under £20 ... but Three is the worst network -they have too many customers on at the same time and sppeds go down in the evening - depending on where you are. I recommend 1pmobile - it is one of very few subnetworks of EE, and you can get PAYG data from them on the EE network, cheaper than EE. Their deal for 200gb for £20 is very good, and no contract. I have never used O2 or Voda, but they are average from what I read. 

MIFI - I am not a fan of the little mifi boxes - they do need external antennas - and expensive adapters for their tiny antenna sockets - so what's the point. I would go so far as to say that a mifi box is a waste of money in a motorhome - you might as well use a phone hotspot. The only practical use for a mifi is for  travellers who live from a suitcase in hotel rooms etc. Mifis are also battery powered from USB, and tey don't like being plugged in 24/7. But if you already have one, and you are happy enough, then it ain't broke so don't fix it - not everybody is a speed crazy internetaholic like me!

Update for 2023. I have been experimenting with 5G, and it has either been not available, or just as fast as 4G and only occasionally super high speed - ie over 100mbs. The bottom line is that 5G is mainly in cities and big towns, and while I am sure it will eventually replace 4G, just as 4G has replaced 3G, for now, I just can't see the point, and 5G 12v mobile routers are still expensive - well over £100. After 3 months I sold it for £20 less than I bought it for and went back to 4G. 5G is nothing special - 4G is and always has been fast enough to deliver an internet TV service - Netflix etc to a motorhome. Only working professionals in technical need of over 100mbs need to consider 5G in a van. Most new phones are now 5G - mine is, but unless I am in a town I never see it connected. But when I have been in a city I have noticed it can be amazingly fast - but in reality the extra speed makes no difference to daily use. All most van owners need is streaming TV netflix etc, and 4G is more than fast enough for that. I streamed Netflix and Iplayer for years on 3G before 4G arrived.

EDIT 2024/2. I have had a dome MIMO antenna on my roof since 2015, but I have not used it for many years since I bought a B525. Recently I was on the roof and noticed it was damaged, probably by a tree. This is what I found inside. I know it looks weird but I do have some training in antenna design, so the use of aluminium sheet is not unusual - the shape gives more bandwidth, but bandwidth does not equate to signal strength - only multiples of a wavelength can do that. But the build quality is awful, using foam and glue - totally unsuitable for the vibration experienced on a van roof. I bet that the internals collapsed long before the case was broken. Electrically - ie in terms of radio reception, the antennas inside this dome are no different to the same size antennas inside a B525 or similar sized router - which explans the very little difference in performance. But that is not to say all roof mounted antennas are bad - only this particular type. See photo below.

These are typical QOS numbers from the admin page of a B525.

Big antennas like these are the secret of of good mobile reception.

Inside an old broken MIMO roof antenna

How a 600ah lithium battery setup has changed my motorhome full-timing life.

But let me be honest from the beginning - very few people will actually need 600ah. I was actually planning 300ah, which was a meaningful upgrade from my original 200ah lead acid setup. But at the last minute a friend who was advising me said that for what it will cost - all other installation costs being the same, an extra £600 to double the capacity was, on paper, a bargain. Furthermore he said that he had found, with that much power on tap, that there were many more intangible benefits that would crawl out of the lithium woodwork. And he was right!

Background - my wife and I full time in our S700 in all seasons. We are also heavy power users. TV and laptop are on most days, most of the time. Our daily power use varies but averages about 75ah a day. Our original fully charged 220ah  lead acid battery, backed up with 500w of solar, would, in winter, just manage a full weekend off grid, with no engine charging or EHU. In summer we had power to spare, and could stay off grid almost indefinitely. But for full timers, it is winter performance that matters.

In winter, our routine was always different to our summer routine. In winter we needed to drive more, and plug in more, which meant using camp sites or visiting friends more often, or even occasionally running a generator. We never liked using it, but occasionally - maybe twice a year, it was a life saver.

Of course there is also the point to be made that you can always use less power - this is a valid point, and we can and do switch things off if we want to stay put for longer and eke out the battery, but it's no fun.

This last system, we ran for about 5 years, and it taught us a lot about energy use in a motorhome. We discovered 3 things. 1. accurate monitoring is essential - you need to know what you have and what you have left - same a the van fuel gauge. 2. No matter what, every amp you take out, has to be put back in. 3. Solar power is by far the most important part of any off-grid system.

1. Monitoring I have blogged about elesewhere. It's important. But I would add that in the context of lithium batteries, you usually get it for free - in an app, and this has proved to be a real benefit.

2. This sounds self evident, but is really important! In summer, a decent solar system will put in the next day all you took out the night before. But in winter, solar panels give a fraction of what they do in summer, so you have to monitor very carefully and plan your activities to put back in power from other sources.

3. Solar power is the only free source of power, and the only one you can be truly off-grid. So in a nutshell, you need to fit as much as your roof will hold.

The reason I make these 3 points is that having a huge battery is not the simple answer to all these problems. But what it does do, is give you options.

One example of this is that with 600ah on tap - whereas before we would have to move after 3 days - now we can stay for much longer. If we use 200ah over a weekend, we still have 400ah left. However we soon learned that if we do stay in one place and use say 90% of a 600ah capacity, then we really need a proper recharge. Winter sun would take weeks to recharge that much, so the reality has proved that if we do need 500ah of recharge, the only meaningful option is to plug in. So our EHU charger has to be capable of completely refilling a 600ah batter in an overnight charger - this basically means 10 to 12 hours at 50a. So another rule we have learned about big lithium, is that your EHU charge source needs to be big enough to recharge in less that 12 hours - ie overnight.

The same goes for alternator charging. A lithium battery will suck in every amp that you throw at it, so a 60a alternator will deliver exactly that, for long periods of time, and will eventually overheat. There are various ways to improve this - we chose to install a B2B - battery to battery charger. This is a unit that sits between the engine battery and the lithium battery, and limits the power that can be transferred. In our case this is 60a - half the capacity of our 120a upgraded alternator. A side effect of this is that with a 60a b2b, 2 hours of driving actually gives us 120a. This is quite different to our old lead acid battery, which would suck in high power for a short while, and then settle down to a fraction of that - so a 2 hour drive would give something like 30a of charge, even though 60a was theoretically available. This is quite technical, and down to the difference in charging characteristics of lead acid and lithium, but this is a noticeable example.

This also a good example of how fitting a lithium battery means that you also have to think about, and if necessary modify, your charging equipment. Lithium batts have different charging characteristics to lead acid batteries. In our case this proved to be a good thing, because as already mentioned in the past, especially in winter, we had to plan our movements carefully, especially with regard to the weather, and driving distance - now we have a decent B2B, we can drive less for the same power, or get more power from the same drive. So when we are just touring around, distance between stops can be less, saving diesel. It also means that with a 50a EHU charger, we can take advantage of even short stops where EHU is available - ie at friends etc.

But by far and away the biggest advantage for us has been simply the fact of having all that power on tap. We no longer have to move because we have to - we move because we want to. We can stay a week or more instead of just a weekend, and if we do, and use almost all of that 600ah - then we know that all we need is an overnight charge, and we are good to go again. In pure financial terms, with campsites and CLs costing around £15 these days, in winter we are saving around £60 a month. 

There have also been some minor advantages, but satisfying nevertheless. We now run our fridge on 220v while driving - this keeps it cooler. And in summer we run it on 220v quite often, even though it is a 3-way fridge and takes 10amps. This is saving us gas - LPG, and we have already noticed that we are using less gas. I have always defended 3-way fridges because they are the ultimate in versatility, and they are. Our 3-way is quite new, so no intentions of throwing it out for a compressor fridge, but if the situation arose, I would now have no problem handling a compressor fridge, even in winter.

Another advantage is the use of high power items. My old system was easily capable of delivering the 100a or so needed to run a toaster or coffee machine for a few minutes, and on paper, because they were only on for a few minutes - eg 100a for 5 mins = 8.3ah - not a lot. But over the months I soon noticed that regular high power use was changing the characteristics of my lead acid battery. I looked into the technicalities of this, and learned that the capacity (and long life) of a lead acid battery depends entirely on the type of discharge it is asked to perform. It will last longer with only light discharge, and shorter with heavy discharge. And because I have accurate monitoring, and am a bit of a geek, it didn't take me long to realise that these morning coffee and toaster sessions were affecting the battery noticeably. 10 minutes of breakfast use was taking much longer to recharge from solar than the numbers would suggest. So after a year or so, we stopped, and went back to gas for toast and coffee. No such problem with lithium - they are quite linear. Doesn't matter if you take out 100a in 1 hour or 1a in 100 hours - the result is the same. So although the basic rule of put back in what you take out still applies, there is no worry about affecting the life of the battery.

Don't forget what I said above - these are minor advantages, but I have enjoyed discovering them and experimenting. 

So do you need 600ah?? Probably not is the honest answer. But several of us full timers have, and nobody yet is regretting the extra cost. 300ah is probably a meaningful upgrade for most van livers upgrading from 100 or 200ah lead acid systems. My system is now 6 months old and I have yet to go below 300ah, but I know it's there, and I expect to be using it for the rest of my van life - 10 to 20 years - which is another good reason to go lithium - long life.

There are 2 ways to get lithium. DIY or ready made. I chose the DIY route. The DIY route involves buying the individual 3.2v Lifepo4 lithium battery cells, and connecting them together, in a case or frame of your own construction, to the power and voltage you want. So in my case I used 8 x 3.2v 300ah cells, in a 4 series 2 parallel configuration, giving 600ah at 13v. The mechanics and connections was a relatively easy DIY job. A lithium battery consisting of multiple cells needs a circuit board called a BMS - Battery Management System. This is a board that sits between the cells and the outside world. It has multiple functions - it balances the cells, and protects them from over and under discharge and voltage. It is an essential part of the system. Good BMS also have bluetooth built in and come with an app. That is all the technical detail I will go into at this point. But anybody with a multimeter, who knows how to use it, has hooked up batteries and stuff before, and is willing to read online from the many excellent DIY websites and forums - is capable.

The non DIY route is to buy from an established battery manufacturer. These companies do what I have just described above, but in a much more user friendly way - ie they put the 4 cells and the BMS inside a box that looks and feels like a traditional 12v battery. These can usually, but not always, be straight swap replacements for old 12v lead acid batteries - but you should check with the supplier. You also get UK based support backup and warranty. A typical example in the UK is Roamer batteries, who consistently get good reviews. But the cost difference is about 50 to 100% over DIY, because you have to pay their profit margin, which is well deserved!

Lastly - order cells directly from China at your peril. BMSs are usually OK, but ordering small quantities of lithium cells can be a nightmare from China, using Alibaba etc. Just take my word for it, and don't be tempted by what appear to be really cheap prices in dollars - that is only the beginning of it. Contact me more more details.

  

MERCEDES OM602 FAN BELT FIT

 This engine is found in most Merc S class classics - late 80s to 1995. I am not sure if the same arrangement is found on earlier or later engines.

I have now had to be recovered in my S700 4 times in 23 years, and 3 of those were for broken fanbelts. 1 was random, 2 a coincidence but 3 is definitely a pattern. It is probably a service item and should be changed every 50k or so - I don't know, I don't have that info. But the reason it rarely gets done is that it is an absolute pig of a job. I know this to be true because I have been witness to the grunting and swearing that has emanated from the garages I have used, plus the posts I have seen on other groups.

So if you have a Mercedes, take note of this post, which will be in the index, for future reference.

All the difficulty stems from releasing the tensioning roller in order to slip on the new belt - at first glance there seems to be no way of doing it.

The first thing I discovered is that most of the online information, and in particular the Russek manual, is either wrong, or at the best, ambiguous. The diagram in the Russek manual is accurate in the general layout, but lacking in detail. After the event, I managed to find much more accurate diags - see below.

The procedure is as follows. Identify where is the tensioning spring, which runs parallel with the hydraulic damping cylinder. Here you find a nut (3 - yellow arrow) which is located on a bolt, which appears to be attaching the top loop of the spring to the bracket. This nut has to be taken off - but if you try, the whole thing just spins. What you can't see, and what isn't explained clearly is that there is a hex bolt head at the other end of the bolt (6 - red arrow) - but where is it? It isn't obvious. The bolt is actually a 3 inch long bolt that goes into a hole in the top corner of the engine block - the hole is about 3 inches deep, and the head of the bolt is back there - you have to reach your fingers in to feel it, and you can just get a spanner on it. One you do, then the front nut removes easily.

Then you have to insert a bar/lever into the recess in the top of the spring bracket - this is depicted in the diag with arrows showing the direction to push. This bar has to be provided by you. By moving this bar to the left or right you can move the spring bracket, release the spring tension, and then using a drift (anything handy) you can then push the bolt back through the bracket and into its hole - you can also help it out with your fingers round the back - but don't take it out completely - just enough so that it no longer fixes the top spring bracket in place. Once this is released, the spring will lose tension, and the tension pulley will fall down a couple of inches, finally allowing enough slack to get the belt around all the various pulleys. It is still a tough job, but it will go on.

The blue arrow indicates the actual pivot point of the bracket - for info only, it has no function in the job.

It is also worth mentioning that there are 2 ways to approach the job - access is really tight, and that is half the problem - you need a good set of tools to get at that nut and bolt. But if you take the radiator off, the job is a whole lot easier. Taking the rad off is a 20 minute job. If you are doing this job yourself, and are not pushed for time, and maybe doing other work, consider removing the rad.

Once it is on, you have to re-tension the spring and then lock it back in place, under tension. To do this, you have to push your bar, which is still in its hole, well over to the left, which will pivot the top spring bracket anticlockwise, until the point where the holes in the bracket and the engine block align, and you can push the bolt forward, through the holes, and the spring is then tensioned and locked in place. Replace the nut, and that's it, job done. When you know what you are doing, and you have just the right sized bar, it's a 5 minute job. If you don't, then it's a frustrating episode with much swearing and skinned muscles.

The confusion arises from the fact that removing the nut is counter intuitive because you think that is what is holding the spring in place. It is and it isn't - the spring is held in place by a collar in the bracket, and the bolt slides through the middle to lock it in place. the actual pivot point of the racket is further down.

I just had to pay a French garage 2 hours labour because they had no clue, despite me presenting them with photos from my collection, and the Russek manual. In the end what saved us was a telephone call to my own mechanic friend in N Wales.

None of this will make the slightest sense to anybody! It doesn't apply to Fiat family owners, and it is of no interest to Merc owners, until it happens to you - at which point, this detailed description should be useful to you or your garage.

I am also now reasonably convinced that in motorhome use, Merc fanbelts have roughly a 5 to 8 year lifespan - probably nearer 5, especially if you have modified electrics, like I do - ie big batteries. In motorhome use, the alternator works harder and hotter and so does the belt. The belt can get damaged slightly if the engine is turned off when the alternator is hot, and the belt can get slightly "cooked" at that point. The alternator pulley is the smallest on the belt, and therefore is working hardest. My intention now is to make sure I have a new belt either every time other work is carried out at the front, or every 4 or 5 years.

Fridge not working on 12v or leisure battery not being charged while driving - how to troubleshoot. The D+ line explained.

This article is about pre 95 vans - with the old style fuse panel, and no Electroblock (EBL). However if you do have a later van with EBL, there is useful info here so it's worth a read. See note at end about EBL.

Fridge not working on 12v while driving is quite a common fault - usually a bad connection caused by old age and corrosion. It is closely related to another fault - leisure battery not charging while driving. 

How it works.

There is a red cable that leads from the positive of the engine battery (EB) to the Hymer fuse box. On most vans there is a big inline blade fuse of 20 or 30amps and although this is not famous for blowing, it can happen, so it needs to be located and checked before anything else.

This red cable then leads to the 2 relays in the fuse box. These relays only operate when the engine is on, so that the flow of power from the engine battery and alternator only works when the engine is on. The relays are operated by a wire from the alternator known as the D+ wire. When the engine is running, the alternator is spinning, the D+ wire goes up to 12v, and this operates the coils in the relays, which close the relay contacts, allowing the power to flow through the relays to both the leisure battery (LB) and the fridge. When the engine is switched off, the 12v on the D+ wire goes off, the relay coil relaxes, the contacts open, and the power is disconnected. This ensures that the EB is disconnected from the LB and fridge when the engine is not on, ensuring that the EB can not go flat, even if the LB does. It is a fundamental feature of all motorhome electrics - also called "split charge relay" - the charge is split between the EB and LB, but only when the engine is on.

The D+ wire which operates the relays, also operates the ignition light on the dashboard - in a normal, non motorhome commercial van, this is part of the original Fiat or Merc wiring.  In order to make the D+ wire operate the additional relays for motorhome use, it was necessary for Hymer to "tap into" this wire. To do this they added an additional yellow D+ wire extension of their own, connected to the original D+ wire, and leading to the Hymer fuse box where the relays are located.

This is a general description - the principle is always the same, but there are differences between Fiats and Mercs, and different models and different ages. But all vans share the 2 common basics - the thicker red wire from the EB+, and the thin yellow D+ wire to the relays. All you have to do is locate them in your particular van.

In Fiat family vans, the EB is located under the bonnet. The red battery cable has to run right across the engine compartment to the other side, where the Hymer fuse box is located, usually by the drivers left knee (on a LHD van).

In Mercs, both the EB and the LB are located in the battery box by the side of the drivers seat.

In both vans, the wiring colours are always the same - red cable leads from the EB+, to the fuse box, through the relays, and back to the LB+ in a black cable. There is also a brown cable to the LB- negative. Do not get the cable colours mixed up! Brown is negative in Hymer 12v electrics.

Troubleshooting

The first test is easy - you need to know if it is all working or not. Disconnect the black cable from the LB+. With the multimeter set to DC volts, place the black meter probe on the negative post of the battery - ie ground - and hold the red meter probe on the end of the black cable. There should be around 13v there with the engine running, and nothing with the engine off. If you have 13v here with engine on, then everything in the charging, relay and D+ side is working, and the problem is elsewhere. If there is no 13v here with engine on, then see below.

If you are troubleshooting fridge not working on 12v, then the test for that is to locate the fridge fuse this is the first fuse below the fuses that are all connected by the copper bar - the top 3 or 4 fuses - it varies from van to van. But the next one down is the fridge fuse - so it's either fuse 4 or 5. Again, with the black probe on the battery negative, and the red probe on fuse 4/5, you should see 12v with engine on, nothing with engine off. If you have no 13v here with engine on, but you have 13v with engine on on the main black wire to LB+, then that means it can only be the fridge relay - the smaller one of the two.

If you have no 13v at these two points with engine on, then the problem lies either with the main red cable, the D+ wire, or the relays. The relays are the least likely cause, they rarely fail.

So the next thing to do is to expose the inside of the fuse box, to do this undo the 4 screws in the surround, and work the box forward - it can be awkward, there are a couple of screws protruding that you can't see which try and prevent the box coming fully out, but if you work the box up and down, it will come, and there is enough slack in the cables at the back - because that's how it went in in the factory.

Once you have the box out, and can see the relays, then the next test is also simple. Get your ear close to the relays, and rest your fingers gently on the relays, then start the engine - there should be an audible click and vibration of the relays operating - relays are switches, and they make an audible click. If you hear and feel this, then that proves the relays are working. If the relays are working, then the problem then must be in the main red cable feed from the EB+. This is rarely a problem in Mercs, because the cable run is short and inside the van, but in Fiats it has to run right across the engine compartment, through the bulkhead and into the back of the fuse box. So you need to locate this cable and check it. The usual culprit is an inline fuse which is either blown, or corroded. Failure of this fuse, its holder, and connections, are quite common in Fiats, rare in Mercs.

For those that don't know, this is what an inline spade fuse looks like - this is a generic pic from the internet, your will look similar, not exact, and may or may not have a cover.

But if the relays are clicking, but you have no 12v on the black wire to the LB+, or to the fridge, then the fault has to be between the EB+ and the relay.

If the relays do not click, then most likely you have a D+ problem, which is a break or bad connection in the thin yellow D+ wire. If you look closely in the box, you will see the yellow wire going to the socket of the big relay, and then an extension, also yellow, going to the socket of the small relay. If there is no 12v on the D+, the relays won't operate - they won't click.

In this photo you can see the yellow D+ wire going to the base of each relay.

As mentioned above, Hymer had to install an extension to the original D+ wire, running to the fuse box. On many vans they used a blue plastic connector called a scotchlock - also called Scotcklok, or snap connector. This is a connector that allows you to easily connect a new wire to an existing wire, without cutting.  

It is very difficult in just words to describe how these look, and work, so the best thing to do is to watch this Youtube. It shows exactly how they work.

https://www.youtube.com/watch?v=9U0N_BFHyaY&ab_channel=CURT

A typical example of the Scotclock D+ tap connection. Most pre 95 Fiat family vans are similar, but you have to root around to find it, and it might not be identical to this photo.

Unfortunately Hymer didn't know back in the 80s and 90s that these would corrode after 20 years and cause problems - but they do. So if you have no D+, you have to trace the yellow wire and look for this connection, because most likely it will be that - it's quite a common fault. The only problem is that with so many vans over so many years, not all vans have one, or it might have already been "fixed" by a previous owner. There is also a possibility that the fault is where the D+ wire is actually connected to the back of the alternator. I can't be more specific - it varies from van to van, but if your relays ain't clicking - it's that pesky yellow wire - somewhere!

If you do discover that the Scotchlock is your problem - then what do you do? The quick and dirty way is to snip all the wires - 3 ends - strip them back, twist together, and then seal with tape. This will get you going again, but will eventually fail after more years, depending on how well you did it, and how wet and damp it gets. Basically you can use any method that reliably re-connects the wires. Choc block connectors, Wago connectors, and 3m have upgraded the original to make it better - the new ones are round and better sealed. there is no one and only way - it's simple electrics - you just have to connect all 3 ends as best you can so that the power flows again.

As already mentioned - the relays are usually reliable and not faulty. But it is not unknown for them to fail. If you are sure that the feeds to the relay are present, but not getting through, then you have to remove the relay and test or replace. But you must be sure - relay failure is quite rare - it's usually always something else. Fortunately these are standard automotive relays, available everywhere. So you either borrow or buy a new relay, change it, and see if the problem is fixed. 

The relays can be hard to remove - work them out slowly by rocking side to side.

Or you can test the relay with a meter. To do this, you need to know how to use your meter to test continuity. All relays have the same pin numbers, which are marked on the relay - 85 86 87 and 30. Pins 87 and 30 are the relay solenoid coil. When 12v is applied to either of these pins, the other pin is permanently connected to ground through the socket, then 12v flows through the coil, which then creates magnetism in the coil, which then forces the other two pins 85 and 86 to be connected. So 85 and 86 should be open circuit when the relay is "off" and connected together with the relay "on". So how do you test this with the relay in your hand? The easy way is to get a PP9 battery - the small rectangular 9v battery that you can buy anywhere - and touch the battery terminals to pins 87 and 30 - the relay should click. If it doesn't, the relay is broken. If you know how to use the meter to test continuity - it's too long winded to explain this here because there are so many different meters - then pins 85 and 86 should be open circuit when off, and closed circuit when on. But 9 times out of 10, if you don't get a click with the battery, you don't need to go to the trouble of testing continuity with the meter - just replace it.

As with most things - there is a Youtube - this short Youtube shows exactly what I am trying explain with words!

https://www.youtube.com/watch?v=UBpQJ1DRa9A&ab_channel=Wisdom

The big relay is the main split charge relay that allows engine power to the LB - the original is a 70 amp relay. This is quite a rare size - it doesn't really need to be replaced with a 70 amp relay, it's a typical case of Hymer belt and braces - they used a big relay value so that it lasts a long time because it isn't working so hard. In normal use the relay rarely passes more than 20 amps. So if you can't get a 70 amp, any value above 40 amp will do. The smaller fridge relay is usually 20 amp and the fridge takes around 10 amps on 12v.

The original relays usually had metal covers - modern ones are usually black plastic - either will do.

So now we have explained how the power is connected from the EB to the LB and fridge, through the relays, and how the relays operate. 

So the only thing left to explain is what to do if you have a working relay system, and you have 12/13v on fuse 4/5 with the engine running, but the fridge is still not working. Well in this case, the problem must be with the fridge. The 2 commonest reasons for this are corroded connections at the fridge end of the 12v supply wire from the fuse box, or the actual fridge switch itself. Just look at this photo - that's how bad corrosion can be. Remove the bottom external vent to the fridge, and check behind there, looking for a connection like this, using the flat plastic covered spade connectors. That is how most classic Hymer fridges are connected to the 12v supply from the fuse box. In this photo the 12v from the fuse box will arrive here, but go no further!

Don't forget - Hymer 12v electrics - blue is positive, brown is negative.

The next most likely cause is the fridge 12v switch itself. These switches don't get much use and spend long periods in storage, unused. Over the years the contacts inside the switch can get corroded. So one trick is to work the switch many times - on and off until your finger hurts. You might get lucky and the fridge switch comes back to life. If you are lucky, sometimes you can pull the switch forward and there is just enough slack in the wires to get at the back of the switch for further tests, or even replacement - but it varies from van to van, as I have often frustratingly found out.

Unfortunately if none of this works, further checks and tests mean getting access to the fridge, and unfortunately this means the fridge has to come out so you can get at things. 

The 12v element in the fridge is quite famous for not lasting more than about 30 years. But to get at it - you need to take out the fridge. The element is a simple heater element - if it breaks, it will show open circuit with a meter. There are Youtubes and other online explainers on this.

EBL vans. 

If you have a later van with an EBL, then here are some notes to help you. On these vans, the relays are inside the EBL, and the main red EB+ feed and D+ yellow wire go into the EBL and the 12v feed from the EBL to the fridge is also there and easy to test. Although you can't get at the relays without going inside the EBL, you can troubleshoot, because the connections are on the front of the EBL, and you can shove the needle of your meter probe into the back of the plugs to take readings. There are different EBLs, but the diags and pin numbers are all online so all you have to do is find them. The D+ is quite easy because it is yellow. So the first thing to test on an EBL is that there is 12v on D+ with engine on. You should also be able to hear the relays if you are lucky. 

But all the above description about the feed from the EB and the way the D+ is tapped into, also apply to EBL vans, as do the comments about working on the fridge itself - the connections, switch and element etc.


HYMER CAMP NOTES

If you have a Hymer Camp, then all the above still applies, but you won't have the Hymer fuse box described above. In a Camp, the relays and habitation fuses are under the passenger seat, and the red cable main feed from the engine battery, and the D+ wire, lead here first, to the relays.

The Classic Hymer meter panel - explained and maintained.

This article applies to pre 95 vans, with the classic fuse panel, and no Elektroblock. If you are unsure - ask on the group.

Most classics have a panel with 2 meters. One marked "Spannung" and the other "Strom". This is German for Voltage and Power. Next to the left meter, voltage, is a switch marked Battery 1 and Battery 2. It's a rocker switch. When you press either way, then the meter should light up, and the needle will indicate the voltage of the battery. Battery 1 is the VB, and should never change when you are parked up, and battery 2 is the LB, and this will very gradually reduce from over 12v to below 11v as you use the power from your LB. You will see that the dial is calibrated not only in volts, but in green and red zones! You should avoid running the battery into the red zone. In fact, by modern standards, the red zone starts a bit too low, you shouldn't really run a battery below 11.5 or 12v. But the old Hymer meters are not as accurate as modern digital ones, so there is a bit of leeway.

You can get some indication as to the health of your battery by looking at the voltage meter, but only when the battery is "resting" ie not being charged or discharged. So if you have solar, wait until night, and not on EHU. A fully charged battery will "rest" at 12.8v, around 13v, and will fall to around just under 12v as it discharges. So in the evening, when you are on battery power only, you can get an indication of how well your battery supplies your needs. If it regularly is at under 12v by bed time, perhaps after you have been using a TV or something else, then maybe it's time to look at your system - regularly discharging a 12v battery to 11v or 10v and below will shorten its life.

The right hand meter - Strom - has the needle always in the middle - known as "centre zero". Green zone to the right of the needle, and Red zone to the left. If the needle is in the red, then you are using power. If the needle is in the green, then the LB is receiving power by being charged. With the engine running, or on hookup (more on hookup later) then you should see the needle in the green. There is no control of this meter - it is for info only. But by looking at it when you switch things on and off, and comparing it with the voltage of Batt 2 (LB) you should over time get familiar with the power system in your van, and it is good for troubleshooting. It is calibrated in amps, but again, it is not very accurate by modern standards. The main thing is that it should deflect either way to indicate charge or discharge, but bear in mind that this will change according to the state of charge of the battery - if the battery is fully charged then don't expect to see the needle deflect much into the green, It will only do so if the battery needs and is receiving a big charge.

Also note that if you have solar panels fitted, the charge from these may not be indicated by the Strom meter. Solar panels were not a factory option and were often fitted direct to the battery, and not via the meter.

While you are hooked up to EHU, the voltage meter will be up above 13v all the time and the Strom meter will generally stay in the green all the time.

On the very left is a switch marked Frischwasser/Abwasser - this means Freshwater/Greywater and when pressed will indicate the level of either the fresh water tank, or the grey water tank. The lower part of the meter is calibrated "leer" 25% 50% and 75% and "voll". leer = empty, voll = full. It is not a continuous display. The level is not driven by a float as in a petrol tank on a car. There are 4 sensors in the tank, so the needle will jump between the 5 positions. It is only a rough guide. In old vans this system often gets clogged with dirt and stops working after many years.

In the middle of the panel you may see the  "switch with no name". This is an extra switch for options and/or owner fitted modifications. Yours may or may not do something. On many vans it has no function. Next to this is often a switch named "Lufter". That means fan, and operates the fan in the space above the cooker, to extract cooking smoke. There should be a lever under the panel which opens and shuts an external vent. 

On the right there is a usually a light switch called "Licht" which operates the kitchen light. On many vans there is also a switch by the entrance door for this light - similar to the two way switches that operate the landing light in a house.

On most classics, the whole control panel is secured by just 3 screws along the front lip and if you undo these the panel will drop down on hinges, exposing the gubbins inside. Many panels have a clock and/or a radio fitted - this is how you get at it. It also gets a bit dirty in there because of cooking, so you should have a gentle clean around every few years.

Troubleshooting

While the panel and meters are generally reliable - problems do occur, especially vans that have been stored outside for long periods.

Most panel problems are old age related - dirt and corrosion. The switches spend long periods not being used which over the years allows dirt and corrosion to build up inside the switch. So the first job to do is to work every switch hard - many times, on and off, until your finger hurts. While doing this, see if you get any action on the lights or meter. The same applies to the wiring connections on the back of the switches and meters. So you have to carefully pull, and then push back, all the spade connectors on the back of the switches and gauges - this moves the metal and cuts through any dirt and corrosion. Be careful - this is a delicate operation.

Then the next job is to make sure the bottom 3 fuses in the fuse panel are OK - these 3 fuses are the panel fuses. Don't just visually inspect them - remove and replace, same reason as before - possible dirt on the ends.

Further troubleshooting will probably need a multimeter and basic knowledge on how to test voltage and continuity.

Unfortunately Hymer never published a circuit diagram for the panel, presumably because it was made by a supplier - Schaudt, in Germany.

All you can do with the circuit board is to clean the connections as best you can. there is also a glass fuse on there, which I believe is a fuse for the panel illumination. This can also be cleaned and checked.

The bottom 3 fuses are the panel fuses.

Technical Background 

Switches

The switches are a standard switch and are readily available online, but you need to prove that the old switch is actually the problem. This needs basic knowledge and a meter. On all switches, the centre pins in the vertical plane, are the common pins. So this is where the supply is connected. The supply is then connected to either the lower or upper pins depending on the position of the switch. So to test a switch, you have to check for continuity between the centre pins and the upper and lower pins. The hymer switches are double gang - ie 2 switches in one. So each vertical row or 3 pins is a separate switch circuit. So, for example, on the battery selector switch, one set of pins is for switching the actual battery selection, and the other set is to supply voltage to the bulb in the meter, so it illuminates when you press. Some of the switches - the fan for example, only have a single function, so only one half of the switch is used. 

Meters

The meters are also still available, but very expensive - around €80£. So you have to be sure it's the meter, and not the feed to it.

If the strom meter is not in the centre and is hard over to one side or the other, then it is broken, usually caused by some incompetence or overload in the distant past. They are reliable and last for years if left alone, but break easily if mistakes are made.

The battery meter also doubles as a fresh and grey tank indicator.

Panel and Meter Upgrades

Although the panel and meters have a certain attractive retro chic - it can be difficult and expensive to fix and keep working, other than the basic cleaning and connection advice already given. The main information given by the panel is about power - voltage and amps. These days more than ever, you need to know how much power you are using, and have left. 

Digital displays were only just becoming normal in the 80s and 90s, but today they are normal - and cheap - and accurate. Accurate display of 12v voltage is actually very useful and important - you need accuracy to at least one decimal point, preferably two - there is a big difference between 12.2v and 12.8v - points of a volt are important. The original Hymer analog meter simply isn't accurate enough. So my general advice is that there is a place for a digital voltage display in a classic Hymer, regardless of whether the original is working or not. During the 90s, digital displays became standard on all motorhomes.

The same goes for the other meter - the famous "STROM" meter - strom is German for power. This meter should display amps - it is a centre zero meter, red and green. It measures, or rather estimates, the amps flowing into or out of the battery. There is a copper component called a shunt, located in the box behind the fuse panel, through which all power to and from the leisure battery flows. There is a cable from this shunt, through a fuse in the bottom 3 fuses of the fuse panel, that leads to the strom meter. When discharging - ie delivering power, the needle deflects into the red. When charging - ie receiving power, it deflects into the green. The meter is calibrated in amps, but again, suffers from the same problem as the volt meter - old technology and only accurate to about 20%. However this is not to be too critical of it, because its simple function of red and green tells you all you need to know at a glance - you need to know that the battery is charging when plugged in or the engine is on, and you also get a reasonable indication of how much power you are using - usually at night.

The other problem with the original strom meter is that it is difficult for it to display charging devices that have been added by owners and dealers - solar being the main example. In order for the charge from a solar panel to be indicated on the strom meter, it has to be correctly connected to the shunt in the fuse box, which involves removing the fuse box, and a difficult cosmetic cable installation. So as a result, most solar installs are connected directly to the leisure battery - it's easier. And many solar controllers have their own digital display, so although the strom needle doesn't work for solar, you can look at the solar display - assuming it has a display, and is visible.

So all of these issues lead to a general point about meter displays - you can do better! You can install a modern digital battery and power monitor display which is far more informative, and have change from £100. How to do this is covered in much more detail in another article which is linked below.

More info

Article on digital battery monitoring

https://hymers700.blogspot.com/2020/06/battery-management-for-classic-hymers.html

In depth article on the fuse panel and fuse box

https://hymers700.blogspot.com/2019/09/the-classic-hymer-fuse-panel-explained.html

Apuljack Engineering

This is a UK firm who will repair your panel if that's what you want. They also supply new meters - but be sure yours is actually broken.

http://www.apuljackengineering.co.uk/

Switches

The best switches are made by Marquardt, available from RS or CPC, also on Ebay and Amazon. Switch terminology can be cryptic - for example - 

"(On)Off(On) Momentary Large Black Rectangle Rocker Switch 6-Pin DPDT 12V"

I can't post links to suppliers because they soon become obsolete, so ask of the group if you are unsure.

https://www.facebook.com/groups/297054424534823

 

FRIDGES - 3-WAY (GAS) VS 12V COMPRESSOR

There seems to be a rumour going around that for some reason gas (3-way) fridges are both unreliable and/or "yesterday's technology". Nothing could be further from the truth. Gas refrigeration is by far the cheapest and most convenient way for normal van use, and the 3-way fridge is the ultimate in versatility.

It probably stems from the fact that "fridge not working on gas" is a common question - but what people seem to ignore is that this problem usually occurs after 20 years of solid service! Compare that with the life span of the average kitchen fridge.

Whenever somebody asks for advice about a gas fridge, you can always bet that someone else will advise to get rid of it and fit a 12v compressor fridge.

12v Compressor fridges exist because there are situations where gas isn't available - ie in many yachts. They are also getting more use in motorhomes because solar power has greatly increased in efficiency and price has come down. But they are still 12v only - no power, no fridge, so the 12v situation has to be constantly monitored, and even if the roof is covered with solar - there is still no escaping the weather, especially in the UK winter. However in the interest of balance I do agree that there are certain cases where a compressor fridge might make sense. An example of this would be where the owner has higher than average 12v system knowledge or perhaps the van is intended for use much further south - ie winters round the Med.

But spending between £1000 and £2000 for the fridge and possible 12v upgrades plus labour? Compared with fixing the original fridge that will cost between zero and a couple of hundred quid?

My contention is that if you possess a working 3-way fridge, there is absolutely no logical reason to rip it out in favour of a compressor fridge. Gas is cheap and plentiful - and always present - otherwise you would have no cooking or heating.

The 3-way system has been around for donkey's years and is as good today as it ever was. 220v when on EHU - 12v while driving and gas at all other times - always on, beer always cold.