Distribution module, fuses and wiring harnesses

Capt. Mike

We get a number of 'relay' questions on other forums, so I thought I'd try to simplify the relay operations. These are not some deep and mysterious devices. They are a switch. End of discussion -- got that?

Now, the innards: They are an ELECTRIC switch. Two of the terminals take an electric current to turn the relay on or off. Most use the current from some interactive device to turn the relay 'on.' Example -- the relay for a set of driving lights. A small current from the vehicle's high-beam circuit turns the relay on. In European DIN standards, these are usually #85 & #86. Often, #86 just goes to ground.

The other terminals are the device being controlled. A current, often stronger or direct from the battery comes in one side, and when the relay is on, goes out the other to feed the device being controlled. DIN numbers are usually #30 for current supply and #87 to the device. In the lights example, a heavy current & wire perhaps direct from the battery, goes to the lights. Thus they do not run heavy current through light wires and it can isolate the lights from dimming during periods of low battery so they don't waiver in intensity. At the same time, the relay only gets current when the high-beams are on, so the driving lights automatically go out when the vehicle switches to low beams.

Where it may get confusing, is some have two terminals for the device being run. All that is is to allow you to plug in one wire from each instead of splicing or jumping them together.

Sometimes, you can be creative -- as VW was with the relay for the Vanagon fridge. It may "tap" one of the other currents going to the relay to run another device. In the original (no 2nd battery) Vanagon, it reversed and doubled up the power from the battery to run the sink pump even when the relay was not "on."

You can test a relay by applying 12v to the controlling terminals and seeing if it opens & closes the device terminals. You can use an ohmmeter on the device terminals between #30 & #87 in our DIN example. When you put 12v on the #85 & #86 set, it should go to 0 ohms -- circuit closed, switch "on."

Dennis K

New member
I have an 87 Westy that looses battery charge overnight. Sometime both batteries go down and sometime only the car battery. An Elect. repair firm tried to fix it 3 times in each case it would be okay when I drove it out and flat again the next morning. If I disconnect the battery for the car side it stays fine. I plan to to take all of the fuses out and test the + side for drain.. What about the clock circuit? Help...
Dennis K

Capt. Mike

The Bentley has a pretty good primer on wiring and using the schematics pages 97.2-97.6. There is a discussion on "Diagnostic tools . . ." in the TOOLS forum. An ammeter, and preferable an inductive ammeter, are most useful at tracking current draws.

What about the clock circuit? It's pretty simple. Current feeds the clock from the same fuse as the interior lights and goes to ground with the rest of the instrument cluster. Circuits 53, 54 & 79.

Since you indicate that sometimes both batteries go dead and sometimes only one, I'd start with the auxiliary battery wiring & items. The relay that puts them in parallel for charging ONLY turns on when the engine is running as it gets its power direct from the alternator. With the engine off, the battery is isolated. For something to drain both, I'd suspect a problem there. "Second battery" has it's own topic in the BATTERY, CHARGE SYSTEM forum. Since the '87 US models did NOT come with a dual battery, what you have was added aftermarket and may have some improper wiring. There is a tendency by some to want to move things to the auxiliary battery and in doing so, mess things up.

Tim Hannink

New member
"Since the '87 US models did NOT come with a dual battery, what you have was added aftermarket and may have some improper wiring."

There were two Vanagon Camper models available in the US in 1987, the base Camper model and the Camper GL (and a Syncro version of each).

My 1987 Vanagon Camper (the proper VW model designation btw) came stock with two batteries as did all of the non-GL Campers and Syncro Campers of this vintage. It even shows the dual battery setup in the Camper Supplement Manual that came with the vehicle, but it isn't shown in the Bentley manual. It was installed to support the non-propane Dometic RC160E Portable Refrigerator that was standard on this model of Westfalia conversion.

The US Camper GL and Syncro Camper GL models didn't come stock with dual batteries.

Capt. Mike

I'll stand corrected. I thought VW had done away with the non-GL models with the 2.1 Digifant. Thanks, TJ.

In view of that, I'd take a much closer look at the fridge. You might be experiencing a fridge fan that trips and runs without the fridge. Another member reported that phenomena in the FRIDGE forum, I belive the "Fridge fans (external . . ." topic.

(Once you have isolated the draw, it's no longer a subject of this general distribution & harness topic and further discussion should be taken to the appropriate forum & topic.)

Capt. Mike

How can we replace a melted Dashlight Wire/Harness?

7-5-08 02:52 AM
Junior Member

Hi Everyone,

We have an 84 Westy ... still. Although we nearly lost her to an electrical fire the other day. Well it was almost an electrical fire. My wife turned off the power before the fire took hold.... Nevertheless when we got her home and started removing the dash panels, we found that the grey&blue dashlight wire that takes power to all of the dash lights (dash dimmer switch, Rear defrost, lighter, heater controls) was melted over nearly it's entire length. I believe that the short began when one of the heater control arms rubbed through the insulation on the heater dashlight power wire. (I guess I forgot to tell her about that little electrical spark I saw in there last week before she took it out :eek:)

This is where I need some help. Is it possible to replace only this wire (Assuming that it is possible to "unload" what remains of the wire from all of the various plugs and then reload the new wire into them again) or will I have to replace the entire harness? :confused:

Thanks for your Help, Ideas, Condolences.... Simon

Capt. Mike

You won't have much choice as to replicating that circuit -- VW has discontinued supplying complete wiring harnesses of that age.

It is possible to recreate that particular circuit. It will be tedious because it supplies so many dash & switch lights, but it can be done. I'd suggest you get the same color/combination wiring which is called "with tracer" (probably have to order via an electronic supply house or mail order) so as to be able to continue true to the wiring diagram. In the one instance I couldn't find a correct color wire with tracer, I got the base wire color and then painted tracer color bands at about 3" intervals. I can then ID the wire to trace or repair in the future. The OE wire is 20 gauge; I'd probably go a guage thicker, say 18, for the replacment. You don't need the heavy duty insulation; put a section of wire cover or use old-fashioned black friction tape (NOT the shiny black electrical tape; scarce, but I've found at Lowe's & Home Depot) wherever it looks like it will chafe such as your heater control lever.

Also tedious, but a much cleaner job, is to strip wire in the exact spots of the longer piece without cutting. You can then double-up & insert the stripped area into the terminal rather than try to cut the wire, strip the two ends, and try to insert both wires into the terminal. Lay your entire harness length and mark where the terminals will go. Get correct terminals, also from an electronic supply, rather than trying to use generic crimp-ons. They are too large and don't have the double securing tabs like original. On OE style, the inner barrel is for the wire itself; the end two tabs are to fold over and crimp into the the insulation. It makes a much more secure connection, both electrically and for resistance to pull-out. I'd break down and spring for the correct stab-crimp pliers, too. Just squishing the connector with cheap wiring pliers will pull out. A dab of solder won't hurt. Connectors, besides their connection size, are also sized for the wire gauge.

You may find more than one size -- not all push-ons are ¼" -- there are two others, about 3/16" & 1/8". When the wire inserts into a bound harness, just run parallel and wire tie at frequent intervals. You can get very small wire tires so as to keep the job neat and not have big ends. Clipoff the excess. If the wire goes through a multi-connector -- I don't see any on the wiring diagram but that doesn't mean there aren't any -- you can get the special tools to remove the terminals from the block but I doubt it's worth it. You can install insulated bullet connectors at the same point if you think a disconnect is necessary.

The wiring diagram will probably be harder to follow than the wire -- it frequently breaks off at one circuit number to resume at another.
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New member
Replacing a Wiring Harness

I have a 1971 VW Bus that I am restoring for a project. I want to replace the wiring harness and my question is where do I start in the Bus? I'm pretty sure I would start from the fuse box and work my way back, but I'm not sure. Thanks for any help!

Capt. Mike

Fortunately, the '71 has very simple wiring and the diagram in the Bentley is layout replica rather than schematic. Many of your wiring harness will not go to the fuze box, or will only have one lead for power. You'll probably do better starting at your major controllers such as the steering column stalks, instrument panel, and switches. For example, your Emergency Flasher switch has 9 leads, only 2 of which go the the fuse box. Your steering column stalk has none going to the fuse box. The object is to have the group of wires from the major component to run together as a major harness until individual ones have to 'branch off' to reach their destination.


New member
Mystery wires?

Hello 'Captain'
This morning I go out to my Vanagon 1990 and see a wire hanging down under the left side of the engine compartment almost touching the ground. It's actually three wires encased in a black water proof covering. Please bare with me while I try to explain the wires. On the left side inside the engine compartment there's a fairly thick light green wire that enters a connecter and comes out a small black wire. Beside it there are two wires one orange and red and one brown. These two wires also go into a rubber connector and come out as two fairly thin white wires. Now these three wires are the ones encased in the black covering dangling down. These three wires appear to have been attached to something because there is a small bit of broken black plastic attached to the black one. Everything seems to be working when I drive the van although it does seem to be running slightly warmer than usual. I've looked and looked and can't find where these wires were attached to. I’ve gone over the ‘Bentley’ looking for any light green wire on a 1990 Vanagon but unless I’m blind I can’t see even one reference on any schematic with any light green wire. Any help from you would be greatly appreciated. Is it possible these wires were attached to the sending unit which makes the cooling fan come on? The van never seems to get warm enough to run the cooling. That's not quite so, last summer in downtown traffic the fan did come on I think. But since then the weather hasn't been warm enough for the fan to come on.


New member
I was hoping someone would be able to help with my 'mystery wires'. There isn't anyone who will even look at my Vanagon within a couple hundred miles. I hope by driving it I'm not going to cause something to break.


New member
electrical mystified

Greeting all, new the westy world, with our 1986 syncro camper. Took it on its madien voyage to Yellowstone Park, 4 degrees. Ran find, woke up in am, started up van to discover no headlights, no windshield wiper, and the heater fan switch not working. Checked all fuses. Decided to head back to Helena, stopped to for fuel, lights, wipers, and fan working. Went down road, they stopped working. Question-----are they all tied together somewhere ??? do have bentley manual---thanks for any help


New member
dash switch?

I am a new owner, have a 93, pretty good shape and real happy withit so far. question I have is there is a switch on our dash that even our very seasoned mechanic does not know what it is for, it is a factory toggle with an S on it. any ideas?

[Moderator note: Toggle switches were eliminated in the early '90s for safety reasons, replaced with rocker or push-on/push-off switches. There are no toggle switches listed in the '93 Eurovan parts fiche.]
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Start Shouting

New member
This may be a dumb question as it all seems obvious but being a novice I'd love if someone would reassure me I'm on the right track.

I bought a '71 bay westy a bit ago and I'm pretty sure the fuses are all messed up. In the Bentley manual they show a fuse box with red fuses only in 9 and 10 but it's listed as being from a '74. Mine seems to have randomly placed red fuses in 7 and 10-12. Should I replace them like in the Bentley manual? Is there any additional things I should check as I don't know how long the wrong fuses were in there?


I would not just cram fuses back into places just to match Bentley. One of the ...ah... joys of owning a really old previously owned vehicle is any of the PO's may have made undocumented changes.

Begin by getting a good photo of the fuse block. The idea is to document what's there at the start. If you later forget which fuse was where, refer to the photo.

Start at one end of the fuse panel and pull a fuse, look for what's stopped working, and mark down what that fuse controls. Check the fuse for it's rating (5A, 10A, fast or slow blow) and make a note of that. Do the job systematically! Leaping around from here to there to somewhere is only going to waste time and give poor results. So... pick one side of the panel and work you way across. Sure, use Bentley to give you a hint as to what a fuse, in which ever position you're looking at, does. But check everything because maybe someone may have "improved" the wiring.

You didn't say whether or not something is not working. That is, do the lights light, the horn horn, and the fan fan or does hitting the horn flip the windshield wipers? Is there an auxiliary battery in the vehicle? There could be some very good reasons to make changes. Or maybe the PO's just flat screwed up.

Also, it's not enough to put a fuse in a slot. Is it the right fuse? Putting a 30A fuse in a 5A spot may leave something unprotected. Conversely, a 5A fuse in a 30A circuit probably won't last too long.