Fridge problems?

Ron's Technical Tips number -10 degrees

FRIDGE PROBLEMS

It's the time of year when our vans come out of storage and many of us have fridge problems.

What most of us have to remember is that our fridges are quite often original, and that makes them over 20 years old. Not many home appliances last that long, so it's not surprising that we get a lot of fridge problems.

Here in very simple terms is how your fridge works. At the back there is a chimney. At the bottom of the chimney is a gas burner, heat from the flame goes up the chimney and passes into the tubes that contain a chemical, which converts the heat into cold - very simple explanation.

Also in the chimney are two heating elements - one powered by 240v and the other by 12v. So there are 3 possible sources of heat to heat up the chemicals.

The commonest problems are the fridge not working on any of these 3 sources, so we will discuss each one in turn.

Gas. The commonest fault is that soot and or crap falls down the chimney and onto the burner which either restricts the flame, or preventing it lighting at all. This is quite easy to fix, as long as you can get access to the burner assembly, usually but not always through the lower ventilation panel outside.

The next problem with gas is that it won't light. It acts just like a cigarette lighter - you press the button, the gas is switched on, and a spark ignites the gas. However unlike a cigarette lighter, when you take your finger off the button, the gas should stay ignited. This is because there is a safety feature called a thermocouple. This is a little finger of metal that is placed in the flame, and if it gets hot, as it should, then it operates a gas valve that keeps the gas flowing. If the gas goes out, it cools, and shuts off the gas. If the gas lights, but goes out when you take your finger off the button after about 20 seconds, then it is usually the thermocouple. The thermocouple is a fundamental safety feature.

The next problem is no spark. When you try and ignite the fridge there is usually a tick tick sound which is the spark. There is another little finger of metal placed in the burner that allows the spark to jump between it and the burner body, again just like an electronic cig lighter. If there is no power getting to this, or the spark can't jump because of crap and soot in the burner, then it won't light.

Finally - there just might not be any gas at all! After storage with the gas turned off, there may be no gas in the pipes, or it might take a while to come through. You have to be patient. Sometimes it's a good idea to light the cooker to promote the gas flow through the pipes, and do remember to make sure all the relevant gas valves are open.

Electricity. Both 12v and 240v elements work on the same principle - just like a kettle element. Power is applied and the element gets hot. Other than making sure the fuses are OK, there is very little to go wrong and if it doesn't work then usually the element has given up the ghost and needs replacing. Occasionally you get a faulty switch, which can be hard to troubleshoot without access to the back of the switch and the use of a multimeter.

Don't forget that in a correctly wired van, the fridge will only work on 12v when the engine is running. If everything else works fine, but you are not getting cooling while driving, assuming it is actually switched on to 12v, the the commonest reason is that the relay which switches 12v from the engine alternator to your fridge is broken. This relay is usually to be found behind the main habitation fuse panel. You should also remember that the 12v element is the weakest of all the heat sources, so the fridge will be less cool when driving than it will be on gas or 240v.

If the fridge is working but not getting cold, or just getting cold at the top, near the freezer box, then this usually means the chemicals have got separated in the pipes. There are various techniques to try and fix this and Peter Curry is our resident expert. 

There are plenty of how to fix videos on Youtube and lots of previous posts on this group, if you are a DIYer, and we have resident experts and recommended engineers to help you out if you are not.

Don't mess with gas unless you know exactly what you are doing - it is quite an easy job to clean rubbish away from the burner, but anything that involves undoing actual gas fittings or pipes should be done by a trained gas man. Replacing elements is also quite a tricky job.

Finally - we all like to keep our vans original, but fridge problems are one of the commonest problems we find on the group. A temperamental fridge can ruin an otherwise perfect summer trip. Nothing lasts forever, so sometimes it's just best to chuck in the towel and buy a new fridge. The new Dometics are a lot better than their grandfathers, colder and more efficient. I gave in and bought a new fridge last year and we love it. But they ain't cheap! But don't give in unless you have had a proper opinion from an expert.

Stay cool people!

UPDATE - more information about the absorption mechanism by Peter Curry

Never turn your fridge upside down it will just pour all the sludge from the resevoir into your evaporation jet. what people are trying to do when they do this is to remix the chemical cocktail that is the driving force that makes your fridge cold.

There are much easier methods to try first , with fridge removal being a final option ready for rotating the fridge to mix the cocktail.
And even this is done in a prescribed manner and direction.
PLEASE DO NOT REMOVE YOUR FRIDGE AND STAND IT ON ITS HEAD you are taking a chance with the odds being about 35% for you and 65% against you.

If fridge has been stood for a while and will not get cold after being on on gas for 24hrs with good flame and flue then there are two possibilities.

1 the fridge is no good buy a new one
2 the chemical cocktail that runs the fridge has sperated out

These are chemicals that once mixed live reasonably happily in a cocktail but once seperated need some encouregment to join to gether again.
Put fridge on gas and if not single energy selector type, put the mains on as well and turn both to full, leave for 4 to 6 hours then turn fridge to 12v and take the van for a drive down a rough road - you are looking for vibration not bloody great potholes! About 1/2 hour is enough,
Then go home put fridge on gas and leave over night.
We have a 90% success rate with this.

Headlight adjuster conversion

RON'S TECHNICAL TIPS number 3.14 pi ...

If you want to get your Mercedes (and others) headlight adjuster working again, here is the kit to do it. Bookmark it!

http://www.ebay.de/itm/Elekt-Leuchtweitenregulierung-T1-T2-Bremer-Duessel-Mercedes-410D-208D-Hymer-S-LWR-/201545448425

And here is the amusingly machine translated description - I believe that "electricity thieves" refers to Scotchlok connectors, the use of which is a criminal offence in Germany...(well it should be!)

Electrical LWR Conversion Kit Mercedes T1 T2 Bremer

MB 208 MB 308 MB 410 MB 309 MB 310 MB 313

Hymer S Class S 550 S 700

Conversion kit from hydraulic to electric headlamp leveling.

As simple as NEVER !!!!!!!!!

Connect Only together Insert, and Plus & mass.

And all through the pre-assembled wiring harness.

Now with the use of the original knob

which keeps the optics in your vehicle 100% guaranteed.

We do not use electricity thieves !!!

Plus is taken in the fuse box of the low beam control, minus the star distributor under the dashboard

The leveling control is suitable for:

Mercedes T1 Bremer

Mercedes T2 Düsseldorf

MB 208

MB 308

MB 410

MB 309

MB 310

MB 313

Hymer S Class

Hymer Eriba S 550

Hymer Eriba S 700

For questions we are at your disposal.

Tel 06198-502296 e-mail:. Info@leuchtweiten-shop.de

  

 

This makes future heist in the main test,

HU Passed!

   

Here you can see the delivery ______________ use simply glue in the knob

The servo motors are a Swiss brand, have an aluminum shaft for receiving the ball head screws, are waterproof and have to adjust a manual adjustment knob at the back of the headlight basic setting.

Fittingly use for the Ducato 230, 280, 290, Volvo 440/460, Hymer, Mercedes all models with hydraulic leveling control, Fiat all models with hydraulic LWR

Delivery:

2 x headlight range control motor ( new parts ) Modified on a CNC machine for different vehicle types.

1 x Round regulator ( new parts )

1 x use for the conversion original knob.

3 x distribution for cable brown, yellow, brown / yellow (original equipment quality)

2 x cable ties with mounting base adhesive.

3 x cable ties

4-sided color and of course PRINTED installation instructions with pictures and diagram what good is a PDF in the workshop or garage.

Installation is carried out in about 2-3 hrs. For the Artisan somewhat gifted. (Are they talking about us Peter Curry​?!!)

We differ from others:

Because greed is not always Geil!

1. use the glue in the original knob!

2. servomotors are not open to cable to solder because Daduchus

leaks can occur.

3. It works with no electricity thieves because this cable be damaged!

4. Cable with three different colors 1mm Automotive OEM quality.

5. 2 x insulated terminals for + and ground terminal (see photo).

6. Cable ties and base adhesive.

7. Printed color installation instructions and no PDF I somehow self print needs.

Shipping: We only ship insured!

Shipping with DHL Paket in Germany for free.

For shipment delivery DHL +6.90 Euro

Delivery to the following countries: 14,90 Euro with DHL

Belgium, Denmark, Estonia, Finland, France (except Guadeloupe, Martinique, French Guiana, Réunion), Great Britain (except Channel Islands of Jersey and Guernsey), Ireland, Italy (except San Marino, Livigno, Vatican City), Latvia, Lithuania, Luxembourg Monaco, Netherlands, Austria, Poland, Portugal (except Azores and Madeira), Sweden, Slovakia, Slovenia, Spain (except Ceuta, Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palma, El Hierro, Melilla), Czech Republic , Hungary.

Glowplugs - again - Overview ...

Glowplug problems can manifest in all sorts of spooky ways, but the system is quite straightforward and there are only two and a half points of failure. 1. The glowplugs themselves, or their controlling relay box. The half reason is the wiring - ie a wire gets rubbed or worn or damaged - very rare.
A glowplug is nothing more than a miniature kettle element, electricity is supplied to the plug, the element glows red hot, which heats the cylinder which helps the engine start when cold. Just like an electric kettle, after 20 years of use they can get a bit temperamental.
When you switch on the ignition, the control relay switches power to the plugs for a pre-determined amount of time, and lights the light on the dash.
All very simple and straightforward, until things get worn out!
Inside the box are relays, and relays don't last forever.
There is also a simple non computerised sensing circuit that does its best to tell you when there is a problem, but it's only output is the light, so it's a bit limited in the information it can tell you. There is no hard and fast way to tell what the problem is, except that whenever the light comes on when it shouldn't, or doesn't go out when it should, then there's a problem.
The good news is that the system is very robust - you won't automatically break down if you have the light on. The worst case scenario is that the engine won't start on a cold morning, and only then if all the plugs are not getting any juice.
The fix is easy - replace the plugs. A garage mechanic can check each plug with a meter and identify the faulty plug, but what's the point of replacing one - it is only the first one to go. Unless you have documented proof or memory to the contrary, then your plugs in a 20+ year old van are likely to be original. So replace the lot.
If you still have a problem then you have to replace the relay. Mercedes will try and charge you a fortune, but they are about £60 on Ebay, and you can DIY.
You can't blame either the relay box or the plugs for not lasting more than 20 years, so replacement will give you peace of mind for another 20.
But like I said - you can last for months or even years with the light coming on and off....but eventually, usually on a cold morning, you will be stuck.

Can't select first gear - possible gear linkage problem - also applies to any gear.

From Facebook

Hi, can anyone help. I have a S700 on a Mercedes chassis and have a problem getting 1st gear, the previous owner said he had changed a linkage on the gearbox and since then had trouble getting 1st gear all other gears are ok.

OK this should be pretty easy to fix. The crucial information is that you said "ever since" the previous owner had changed a linkage. In my book, that means he fitted it wrongly. The "left and back" first gear on the Merc box has always been a challenge for most, but it should work perfectly with practice - it isn't faulty by design. If you look at the side of the gear box you will see there are several arms about 6 inches long coming out of the side of the box, attached to rods running forward. If you get somebody to go through the gears (engine not running) while you look, you will see how the mechanism works, and you will see by a process of deduction which arm is responsible for selecting first gear.
The arms are attached to the little shafts that stick out of the box. Those shafts are splined - they have little grooves in them, and the round holes in the arms are similarly grooved where they locate onto the shaft. There is a bolt that attaches the arm to the shaft. It is my theory that the arm has been reattached to the shaft just a single groove (or tooth if you like) either way, incorrectly. So you should loosen the bolt and gently work the arm off the shaft, then relocate it one tooth to the left or right - I can't tell you from memory which way, you will have to do it by trial and error, but it will probably be in the direction which results in the arm traveling further, and thus engaging the gear more fully.
Having moved it one groove, either clockwise or anticlockwise, retighten it, and then jump into the van. Start the engine and depress the clutch, and then select first. You should notice straight away if you have got it right - first should select with a satisfying feel, no grinding of gears, and as you lift the clutch you should feel the power go to the wheels, without it jumping out of gear. If not, repeat the process one groove in the opposite direction. It is unlikely but not impossible, that you may even have to go two grooves - depending on how inaccurately it was originally fitted - but the fact that you say it is a problem selecting first gear, and not that you can't select it at all, indicates that it should only be one groove.
Of course I can't guarantee this fix, but from what you have said, and based on my own experience, it is certainly the favourite thing to try first. It is highly unlikely to be an internal problem in the box.
Somebody else mentioned bushes and it is also correct that the plastic bushes on the linkages can get worn, resulting in a similar problem, but on the basis of how you have described the problem, you should try this first.
If you are not mechanically minded, and in possession of a tool box, or at least a spanner, then just pop into your local or favourite garage and explain the problem, plus my comments, and they should be able to do all this in about 15 minutes.

Like · Reply · 1 · 3 hrs · Edited

Ron Bentham This is a picture of a 410D box,  You can see where the arms attach to the box - the opposite end from where the rods are attached. You can see that moving the arm one groove to the left or right on the little shaft will have quite a big effect - it only has to be one groove out to cause trouble.

Further thoughts. It pays for Merc owners to be familiar with the gear linkage mechanism. Many a holiday has been ruined when after a long trip, especially on rough roads, suddenly you can't get a gear, or any gear, and the stick feels like a bag of spanners. The obvious reaction is that the gearbox is knackered and that this is going to be catastrophically expensive, especially if you are abroad. In fact total gearbox failure is extremely rare, and the Merc gearboxes are as good as the engines - I have run them for 400,000km with nothing more than oil changes.

It is the linkages that cause the problems, as I have found out several times over the years. If the gear change is getting stiff, and giving the impression that it just isn't like it used to be, then it is usually just in need of a good clean. It is quite a complex mechanism that converts the movement of the stick into pushing and pulling the lever arms on the side of the gear box. If you look at the pic above, you will see that there is an assembly on top of the box that has the base of the stick sticking up out of it. This assembly contains a lot of levers and linkages that over many years can get very dry and dusty. There is a plastic cover about 3 inches by 2, which when removed exposes the mechanism - photos are hard to come by - it is not shown in the pic above, but if you get under there and have a good look, you will find it. The cover just pops off. Inside of there needs a good clean out and lube. You will be amazed at the difference.

The next problem is the dreaded "knackered box" scare. What has usually happened is that one of the selector arms, as in the photos, has simply worked loose and either started to slip, or even fallen off all together. If you are lucky you will find it still hanging around - if you are unlucky it will be gone, and it's a garage job, but won't be expensive. The problem is that if just one works off or loose, it is likely that the whole mechanism gets out of kilter and you can't select any gear. This happened to me in Italy once and the only gear I could get was third, but it was enough to limp off the autostrada, save myself a hefty fee, and limp to a local garage where they fixed it in 30 mins for 20 euros cash. I could have fixed it myself but it was raining and my back was killing me!

The selector arms attach with a single bolt - as detailed above, and they do have a tendency to work loose over the years. The problem when they come loose is getting them back on in the right position. I am sure there is a Merc workshop manual procedure for this, but out on the road you just have to do it by trial and error. Any decent rescue mechanic should be able to get you going again, especially if he is over 50! 

Finally, another lesser known problem is that where the actual gear stick fits onto that stubby stick on top of the box, there is a rubber sleeve fitted to dampen the feel. This can also get very worn after 20 years, and can also create the impression that the box is sloppy and  "on the way out" - a new sleeve for a few quid (if you can get one!) and the box feels like new again.

So be familiar with your gear selection mechanism and avoid that sinking feeling if it ever happens to you. It is usually always an easy fix, and of course regular maintenance is also important.

About Hymer door hinges

For newcomers - the story so far. Hymer habitation doors are held on by 4 aluminium hinges. Many never have a problem, but it is fair to say that a significant number do. The biggest culprit is the wind catching the door and either slamming it open or shut, and after many years one or more hinges break.
A temporary repair can be effected by using a large washer, but until recently it was easiest just to order spares from Hymer/Brownhills.
Then several years ago the news came out - don't know whether it was true or not, that the hinges were no longer available because the supplier no longer possessed the tooling.
The technical background to this is that in order to produce a hinge with the relatively complex profile of the Hymer one, you use a process called aluminium extrusion. This is where you take a lump of solid machine tool steel and carefully carve it out until you get a hole of the exact same shape as the profile you want - ie hinge shape! Then you harden it in a furnace, and polish it up. Then you mount this special "tool" in a bloody great machine called an extruder which takes lumps of raw aluminium and under huge pressure forced it through the hole in the tool. The pressure is so great that the aluminium becomes plastic and flexible just as it passes through. Then out the other side of the machine pops long lengths of perfectly shaped hinge and all you have to do is to chop it to the right length and insert the steel pins and voila - thousands of little hinges.
This is how aluminium windows are made, and thousands of other everyday objects made from aluminium. The same process is also used to extrude plastics.
The problem is that the tools are very expensive to make - several thousand pounds usually, depending on size and complexity. Usually the cost is borne by the customer, and amortised over the life of the product. So the Hymer people would have projected how many hinges they would need over the life of the design, and divided the cost of the tool by that. Example - £4000 of tooling divided by 10,000 hinges = 40p plus cost of material - probably another 40p, plus labour and overhead say another £1, plus profit and then greedy markup as it goes from manufacturer to Hymer through wholesale and retail and eventually us poor buggers end up paying £20 a hinge!
AND NOW THEY SAY THEY HAVE LOST THE TOOL!! This sounds like it's worse than leaving the baby on the bus, but the reality is that small companies get gobbled up by big ones, things do get lost. Personally, being half engineer myself, I reckon that the original tool was modified to make a different profile, in the mistaken belief that the original tool was obsolete. Or some bloke at Hymer stores had such an enormous bucket of them that they thought bloody hell we'll never shift all these....so they never got re-ordered for many years until slowly but surely us lot used them all up.
So now we are all unhinged ... Hymer understandably don't want to pay out for a new tool because they won't sell enough to cover the cost. They may only sell 1000 over the next 10 years, so using the same formula, That's 40p in tooling, which doesn't sound a lot, but the extruder won't set up the machine for such a small quantity - so the whole job becomes uneconomical.
However it is new news to me from Brownhills that Hymer are maybe going to do something about it - there is a PR element at play as well. So maybe the problem will go away.
Meanwhile, there are other methods of making hinges in smaller quantities, and Peter Curry is looking into this.
My own solution, when my entire door blew off in a sandstorm in the Sahara, and ended up 200 yards away....was to cruise around Moroccan hardware shops until I found a standard steel hinge that did the job. I'll post a photo in a separate post.

TV reception and antennas

The thing to remember about TV nowadays is that since the digital changeover things have improved greatly for campers. The new digital signals are generally stronger, so coverage with a weaker caravan aerial is quite a bit better. However the big difference is that digital either works or it doesn't - not like the old days where you could hear the audio and watch a fuzzy picture.
The aerial that PC recommends, the Status directional, is indeed one of the best, but it is "directional" - which means you have to rotate it for the best signal - usually it will work in any position, but the more remote you are, the more likely you will have to rotate it before you view. If you don't fancy this (and I don't) the same company make an omnidirectional aerial - the one that you see often that looks like a flying saucer - and this works almost as well. When I park up, I just switch on the TV, get it to scan the channels, and if it works it works and if it doesn't then we do something else with the radio or computer. Most of the time it works.
Sometimes you will get channels, but you will see little blocks of interference in the picture, which makes viewing difficult. These are the situations when the directional aerial would have been better. But it is also a useful tip that if you do see the square blocks just moving the van forward or back a yard can make a difference. This is because the wavelength of the radio signals being received is less than a metre, so moving the aerial just a short distance can make the difference between the signals arriving "in phase" or "out of phase".
I have never tried the small amplified aerial in the post by MF, but I have read good reviews - good enough anyway, and not bad enough to advise against. It will work in most situations.
But it is fair to say that the only way to maximise your chances of reception is to have the biggest and best aerial you can afford, as high as possible. Thats why you often see caravaners on sites putting up a pole with a traditional aluminium house aerial on it - they are the best of all.

interesting turbo articles

http://forums.mercedesclub.org.uk/showthread.php?t=122132

http://www.wildcamping.co.uk/forums/show-us-your-van-motorhome/40941-yes-possible-fit-turbo-into-old-hymer-but-do-i-recommend-no-3.html