Reconstituting missing wiring

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ohiowesty
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Reconstituting missing wiring

Post by ohiowesty » Mon Dec 26, 2016 12:01 am

Problem: my '78 Westy is missing the harness for the booster fan.

Description: The relay is still there, as well as the connector coming out of the motor. Below, I found a red wire, with half of an inline fuse holder, which I assume it should go to prong M on the relay. Next to the red wire there is an inch of brown/white wire sticking out of the harness, which I think it's the tracer to the heat lever switch in the dash, and should go to #31 on the relay. I know I have to hook up a yellow/white wire from the fan motor connector to 8 and jump it to J, and then somehow ground the other side of the motor connector. Lastly, run two black wires: one from relay prong A to #15 on the ignition coil, and one from the same prong A to the ignition switch.

I have four questions:
1. where to ground the fan motor?
2. why connect the relay to the ignition coil? I assume that the ignition coil will energize the relay coil (and the dash switch will close the ground side of the circuit). But so will the ignition switch, so it's like having two hot wires on the same prong?
3. I can't locate the black wire coming from the ignition switch. Where should I look?
4. Until I get my hands on original wiring, I am planning to attempt reconstruction using a generic Bosch type 4 prong relay+harness, and generic inline fuse holder. I will substitute as follows: A=86; M=30; J,8=87; 31=85. Are there any caveats I should be aware of?
relay old and new.JPG
Some pictures of the original 1978 wire setup, if available, would be really appreciated.

Thank you
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Amskeptic
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Re: Reconstituting missing wiring

Post by Amskeptic » Mon Dec 26, 2016 8:20 am

ohiowesty wrote: 1. where to ground the fan motor?
2. why connect the relay to the ignition coil?
3. I can't locate the black wire coming from the ignition switch. Where should I look?
4. Until I get my hands on original wiring, I am planning to attempt reconstruction using a generic Bosch type 4 prong relay+harness, and generic inline fuse holder.
1. Ground spade is normally found on one of the bracket bolts hanging the assembly to the ceiling of the engine compartment.

2. The black wire from the ignition switch normally leads directly to the heater relay, then there is a jumper to the coil. Note that the source electricity for the coil is coming from the heater relay spade, not the other way around.

3. Likely at the coil (+) 15 terminal. Bring it to the heater relay terminal, then look for the jumper to the coil.

4. You want a good 30A relay. VW doubled up the 30-87 contacts for better current capacity (i.e. 30-87/87 and they had a little yellow/black wire loop to join the 87s. On the original relay, they did not use the number 87.
Colin

(you can see the ground spade here, and you can see the harness that contains the black wire from the heater relay TO the coil #15)

Image
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 91 414 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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