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