Fridge-water-battery (LED) panel

Capt. Mike

Our topic on LED panels has disappeared in a computer glitch. This topic is for the LED panel on the front of the galley cabinet on Vanagons, the fridge/battery charger panel on late Type II P27's and the E153 display on Eurovans.

John has provided me with text version back-ups of the original topic but as I read them, they refer mostly to owner modifications or individual malfunctions. I am not reposting as they would only be applicable to those members and not contribute significantly to the main body of knowledge.

Capt. Mike

Type II (Bay window):

The P27 campers (AC/DC fridge) had a control panel that served the camper side of the dual battery system. It had a DC test guage for the auxiliary battery. It did not test the main battery. However, when the engine was running and both batteries were in parallel, it read the system voltage -- i.e. the alternator output.

It had two fridge switches -- one for on/off and the other for city (shore) power or auxiliary battery power. They system was such that the fridge would not run off the main but the auxiliary battery charge & thus fridge were being fed from the alternator when the engine was running.

It then had an auxiliary battery charger timer. This was to recharge the auxiliary battery when on shore power. This was a manual charger that put full amps of the converter (~25a) into the battery. It had a maximum setting of two hours to prevent overcharging, but one should use common sense and repeat short intervals, using the battery condition gauge as a guide. It would be rare (and a dead-dead battery) that it would require more.

It would not recharge the main. The charger had sufficient capacity but there was no electrical means to put the batteries in parallel. You could run a jumper cable from the auxiliary battery + terminal to the main's + terminal for recharging; the 2nd ground cable would not be required since they had common chassis ground.

Capt. Mike

Vanagon Campers had an LED panel in the center of the galley cabinet. The left side had a vertical row of LED's to indicate water tank fill level -- green, yellow & red. These fed from sensors at the tank. Depending on year, the sensors may have been on the tank side or incorporated into the internal float.

Below these LED's there was a green LED that indicated the fridge LP pilot light was operatiing. It had a little snow-flake icon next to it. I've had some members report that LED was missing on their models. There is an internal viewing lens in the bottom left rear corner of the fridge.

The right side was a series of LEDs to show the condition of the battery. This showed the MAIN battery in original factory wiring since it feed from terminal 30/fuse S4 of the main relay panel. Again, I've had members report that theirs fed from other sources and thus might read the auxiliary battery. The US models did not come with an auxiliary battery so any so equipped would be aftermarket conversions and thus may have had owner changes to the wiring.

The small toggle switch in the center was to turn the LED panel on or off to save battery when idle. Since the fridge should only be run on DC while the vehicle is in motion & power consumption of the LED's is so low this should not be an issue to a healthy battery system.

The diagram in the Bentley on 97.32-33 covers through 1985 models. There are differences in later models but the function remains the same.

Capt. Mike

Eurovan campers had a Camper Central Electronic Display, near the front interior light. It had sensors such that it would display fridge temperature condition, waste water level and outside air temperature. The Bentley shows feeds from the fridge and shore water, presumably to indicate their status.

The Bentley (X171 & X172) also show other feeds so the panel is used for other non-camper functions. One is the windshield washer level., another the rear defogger.

Capt. Mike

Transferred to consolidate same topic.

martinf Junior Member Posted August 07, 2007 08:06 AM

I've learned a couple of things since buying my Westie that I thought I should share since they took me a lot of sweat to figure out and might
save others the same. #1 The little instrument panel on the fridge cabinet has very useful
information but mine mostly didn't work and I just met another guy with the same problem. It is simple to fix. The vibration of years of use had broken the solder joints at the base of the LED lights. Take it out and re-solder the connections and .. presto!

#2 The ground connection to all the electrics in the kitchen is buried behind the wall liner, behind the cabinetry, behind the fridge. Mine had failed and the water pump and fridge wouldn't work. I fixed it and improved the situation in 3 ways. The electrics work (obviously), the water supply hose from the tank to the pump was crushed under the cabinet
and was only supplying a dribble to the overworked little pump and also, I cut a hole in the wall liner to where the ground connection is.... so I can get at it again in the future. The hole is in the back of the cupboard beside the fridge in the top left area above the shelf.

[Unrelated additional topics deleted.]


New member
My 92 cv has a problem with the central display. With the ignition off it shows low voltage even though the batteries have a full charge or when plugged in to shore power. When the ignition is on the display goes blank. I have gone through the Bentley and found and cleaned all the grounds, have checked resistance, everything seems to be ok. I recently met another westy owner who kindly let me swap my display panel into his westy and the panel works fine. Does anyone have any ideas. I'm at a loss, it's camping season and I'd like to be able to use the fridge.

7/7/09: I started tearing the interior of the van apart to trace all the wires and found another ground connection site which had a broken wire. Looking in the Bentley later I found it as ground 49, which does not appear in the schematics for the central electronic display. Repaired wire and everything has been working properly.
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Vanagon Campers LED panel - switch broken

I have a broken toggle switch on a Vanagon Camper LED panel (1987). It appears to be an ultra miniature on-off-on, although I guess a momentary would also work. I've been searching electronic component places but no luck yet. The panels are NLA from VW.

Mine either got worn out or might have been stepped on a bit after getting out of top bunk. I suppose a replacement panel would do it too, but a little bit overkill. Does anyone have a repair solution or substitute.

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New member
Battery charger panel or 110 => 12v converter problem


I am restoring a 77 type 2 Westy p27. And have a question regarding the fridge/battery charger panel on late Type II P27's

All the camper equipment and secondary battery (and water tap) is now working.

The one thing I cannot figure out is how to get the battery charger to work. It should be able to charge the secondary battery when on city power.

What is working:
-Fridge works on second battery power (red light on panel lights up)
-Fridge works on city power (red light on panel lights up)
-Battery status indicator works

What does not seem to work:
-Battery charging on city power. The way I tested to see if it was working is by flipping the battery indicator switch while it is supposed to be charging. If the charging would work, I would expect the reading to go from "yellow" which is my current battery status to "charging" all the way to the right. (this is what happens if I pull this switch when the motor is running and the secondary battery is being charged).

I suspect one of two problem causes.
a) My timer turning switch is defect
b) my 110 to 12 v converter is defect

Re a) Defective timer switch: I am not sure how this switch is supposed to operate. I suspect once you set it to 20 minutes of charging it should slowly return to the 0 position and stop charging. However, the switch does not move in my case. Also I am surprised that I do not hear any ticking noise when winding the switch (Like a kitchen cooking timer), but again I do not know what normal behaviour is. The last thing which is strange is: I can wind the timer both left and right passed the 0 position.

Would be great if anyone could explain behaviour on a working timer switch and/or has a procedure to test the timer switch.

Re b) Defective converter. Before I go and explore this cause. Can anyone tell me if it is possible that my converter is deffective, but that I still get a red light on for the fridge indicator on City power. I am not sure if the fridge has a separate converter or uses the same one as the battery charger. But if it is the same one and my fridge works on city power, I could rule out a deffective converter. Again, if anyone has a simple test procedure, that would also be appreciated.

I hope I was able to post enough details of my analysis so far.

If anyone thinks of additional info that may be helpful, let me know.

Thanks in advance for all your help.



New member
1990 Westy. 2.1L Auto trans. 248,000 miles. LED in kitchen panel goes from red, to amber at 12.62 Volts. In other words- when I camp, the green LED quickly drops to amber. This is disconcerting!! QUESTION: is this normal? I have only noticed this the last couple months. New Interstate MT-41 battery- 8/09. Shop said radio had a short, draining battery- remopved radio. Battery still drained. Removed fuse for interior light, radio etc circuit. Still drop Voltage. Got replacement battery. Volts still drop quickly to 12.5, amber LED comes on. In this normal??
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Doc Brown

New member
Reverse Engineering the LED panel

My sink pump stopped working, just before my first camping trip of the year! The pump was brand new from Bus Depot and worked fine on my workbench jumpered directly to a 12V supply, so I immediately suspected the tank level meter. I hacked my way through the camping trip by connecting the pump +ve lead directly to 12V (bypassing the meter entirely) but figured that since I have a Ph.D. in Physics and teach electrical engineering I ought to be able to fix the meter panel. I am happy to report that I was able to repair it and I present the following epistle on how it works in case any one else is having trouble with their LED panel.

Firstly, my Westy is an 81 and is a Canadian model, eh? My meter panel does not look like any of the ones shown in Bentley and has some weird 'features'. Anyone else who has taken theirs apart, particularly other model years such as those that have the fridge pilot light LED, and would like to add any information should please feel free to do so. It is entirely possible that my panel was unique in the universe (it certainly is now) and my analysis of its operation is entirely incorrect, since I didn't design it. I suspect that the basic operation of all Westy LED panels is similar.

Secondly, I am assuming that you know something about electronics. If you don't know the difference between a PNP and an NPN transistor, this discussion may not be terribly useful. But if you do, then you will have no trouble understanding the schematic that I drew. Component designations (R1, U2 etc) have been arbitrarily assigned by me and are used in the following discussion. Hopefully the Captain of this ship will add my schematic to his technical drawings and link to it here so that this all makes sense :)

Thirdly, some basics. The water pump receives 12V from the meter panel at all times provided that (1) there is sufficient water in the tank and (2) the switch on the meter panel is switched on. The faucet completes the circuit to ground, energizing the pump, when the tap is turned to the T position. In addition to deciding if there is enough water in the tank to run the pump, water tank level is shown with a 4 LED gauge, and battery voltage is shown with a 3 LED gauge. Bentley claims that there is a pilot light, but not in my van. Also, later model years have a light to indicate that the fridge burner is lit. I shouldn't have one of these, however I do have an unidentified piece of circuitry which I suspect may be for this purpose if only it were connected.

The panel uses two integrated circuits, both LM324 quad op-amps in a 14 pin DIP package. It turned out that one of mine had problems. I didn't have an LM324 handy, but I was able to find a TLC274. Although the '324 is still available from National Semiconductor, Fairchild and probably others (check your favourite online electronics retailer), you can substitute most any 14 pin DIP quad op-amp PROVIDED that it has similar specs to the '324. The most important of these would be that it is designed to be used in a single supply circuit, it can handle at least an 18V rail, it has rail-to-rail output (at least to the negative rail) and that each amp can source or sink at least 20 mA. All 8 amplifiers are used open-loop, rather than with negative feedback as is more common. As a result, they are all really comparators, multiplying the difference in voltage between the + and - terminals by a very large number, but limiting the result to the range 0-12V. So for each amp, if V+ > V- the amplifier output will be 'high' (close to 12V) and if V+ < V- the output will be 'low' (close to 0 V).

There are 5 pads on the solder side of the panel where wires are attached that go to the multipoint connector under the sink (T6 in Bentley). The pads are labeled 1-5 on my panel at any rate.

12V Power arrives at the panel board on an orange wire on pad 2. This corresponds to T6/4 (Bentley 97.32b), this terminal is marked 1 in the multipoint connector shown on page 97.30.

Ground arrives on the panel on a black wire connected at pad 1. This corresponds to T6/6 (Bentley 97.32b), this terminal is marked 2 in the multipoint connector shown on page 97.30. In my schematic all ground symbols ultimately connect to pad 1.

The water tank signal arrives at the panel on a green wire connected at pad 3. This corresponds to T6/2 (Bentley 97.32b), this terminal is marked 3 in the multipoint connector shown on page 97.30.

Power to the pump is provided on a yellow wire connected at pad 5. This corresponds to T6/1 (Bentley 97.32b), this terminal is marked 4 in the multipoint connector shown on page 97.30.

On the panel, 12V power is provided directly to the collector (the case) of Q1. This is an MJ3000, but could be substituted with a similar NPN darlington (such as an MJ3001) in a TO3 case. The most important parameters are probably Ice and Vceo, make sure that they are at least as high as for an MJ3000, 8A and 60V. The emitter of Q1 feeds the pump directly. All other components are fed from the 12V line through series diode D5 (1N4001). I'm not quite sure why this was done. A flyback diode would make sense for an inductive load (like a motor), but that's not how D5 is connected. Adding a 1N4004 as a flyback diode to protect both the faucet switch and Q1 might be a good upgrade, but it could easily be added at the pump itself.

The voltage at the water tank sender is compared to several levels (corresponding to the possible level signals) by the 4 amplifiers in U1. The water tank sender signal is pulled up to 12V through R1, the sensor connects to ground via a resistance that depend on the water level. In my tank, there are 5 metal probes in the side of the tank, the lowest one being ground. Supposedly resistors are wired in parallel to each pair of probes inside the 'black box' on the tank, though I didn't investigate this. The overall sender resistance to ground decreases when more probes are immersed in water. Tanks with a float probably use an electrically similar system but the resistance varies with float position as the float opens or closes switches. The voltage division thus produced is compared with 4 fixed thresholds set by the ladder R2-R6. These were presumably chosen to allow for variation in the conductivity of the water (perhaps you like to drink seawater). If all 5 sensors are immersed, the sensor voltage will be lowest, below the threshold for the all 4 amplifiers in U1, so all will have outputs near 12V. This results in only the green LED being lit. With the top sensor out of the water, the voltage increases above the threshold for the first amp which goes to 0V turning off the green light and lighting the yellow one (the green one may stay dimly lit, too, due to the way it's wired). As the next sensor comes out of the water the voltage goes up again, bringing the second amp output to 0 V, thus turning the yellow light off and the top red light on. When the last sensor is out of the water the voltage is so high that the thresholds are reached for all 4 amps turning the top red light off and the bottom red light on. The low voltage on the last amp is fed to one of the amplifiers in U2 which is set to compare to half battery voltage. Since 6V > 0V this amplifier turns off to 0 V and turns Q1 off with it, disconnecting power from the pump.

The battery gauge works similarly. The battery voltage (or rather a fraction of it set by variable resistor R20) is compared to several thresholds to determine which light to light. The lowest is determined by zener D7 which sets the red-yellow light threshold at 9.1V. The yellow-green light threshold is one diode drop higher (or about 9.7V). If your meter is reading strange, try adjusting R20 so that the lights switch at the desired voltages. This can easily be done with a variable bench power supply and a digital voltmeter. Note that you only have one control to adjust both the green-yellow and yellow-red thresholds. If you really wanted to, you could use your new found knowledge of the panel I suppose you could hack the circuit to allow independent adjustment of both...

The one weird thing about my panel is the red light D11. This is folded over so that it can only be seen if you take the panel apart. And the circuit is such that it will only light up if pad 4, the white wire, is connected to ground through 1M or less or is fed with a <6V signal. Which can never happen because the white wire does not connect to anything in T6/3 in my van! I suspect that it is supposed to be for the fridge pilot light. Does anyone know of anywhere in the fridge that I could get a signal that is low resistance to ground if the fridge is lit and high otherwise? It would be cool to add the fridge light.

Hopefully this is of use to someone. Maybe it will encourage others to reverse engineer other parts of the van and post the results. Incidentally, if your panel is damaged beyond all repair, you could build a new one using my schematic (which I have in digital gschem format) and a PCB manufacturing service...

Doc Brown

New member
Reverse Engineering the LED panel Part II

Hmmm. Turns out that an 18V substitute opamp (like the TLC274) may not be high enough, without adding some capacitor filtering to the LED panel. Don't ask how I know. :(

Best stick with the original (36V) LM324.


New member
Doc Brown,
You mention a white wire you found in the analysis process. In getting my sink pump (1980 Westy) working again after adding an independent second battery, I learned that, contrary to my assumption that the white which is packaged with the thick red is not a ground. Hooking that to ground when I hooked the red to pos made the pump not work. Reading other posts, I started the engine, which allowed the sink pump to run. I read on, then disconnected the white from ground and the pump worked without the engine running. This baffles me, probably because I don't have a wiring diagram to tell me what the white is going to.
Can anyone fill me in on this? If so, thanks!
...Tom in the Chocolatewagon


New member
I have a 1984 Vanagon, has anybody had the fridge Led always on? Even if the fridge is off the light is on.


New member
resurecting this thread

i have an 83 AC with the green fridge LED. my battery LEDs were blinking wildly when switched on and the water level red LED would stay on all the time regardless of the actual water level. i had trouble diagnosing the issue. at first i thought it was was the potentiometer due to random output voltage drop, which i replaced, but that did not fix the issue. next i thought it was the op-amp chips, but before i ordered new ones i decided to clean the board/chips thoroughly to remove all the oxidation. all it took was some very fine sandpaper moistened with alcohol to remove the black oxidation from the op-amp pins (between the board and the op-amp chip itself) as well as slight scraping of the chip with am exacto blade between the pins to remove dirt/grime that may have caused the cross shorts. after that i used compressed air to clean the board (can stuff is good enough) and now it works good as new. try cleaning the chips/board first before you decide to solder or swap the panel. YMMV, but it worked great for me.