Wiper Madness Electrical Mystery - Car Won't STOP

[gte619n]

Hey guys,

I was hoping you could help me track down this last mystery on my e9. I have a 1972 with a fuel injected B30 out of a mid-80s 5er. I've managed to track down and repair all the issues (even my rear fog light!) except for the last one: Wiper Madness.

Here's the situation:
1. Car off, fuse 4 has 0V
2. Turn car to on position, fuse 4 has ~12V as expected
3. Push in Wiper stock. (Wipers don't move)
4. Turn off key, remove, throw into bushes
5. Fuse 4 still has 12V! Car car stays on!

The is especially fun when you go to the valet and he tries to turn the car off.

But here's the other thing, if the car is off and you push in the wiper stock, there's no change. Something is obviously cross wired (relay?) but I can't quite figure it out. I have tried it with the wipe wash control disconnected and the wiper motor disconnected and I still have these symptoms.

Can anyone fire out some ideas about how to track this down? I just can't seem to find anything that's obvious!

Thanks!

PS. Is this the "Wiper Switch" from the electrical diagram? It's installed in the engine bay in front of the motor against the firewall.

 

[HB Chris]

Wiper relay is under dash, I would suspect it's your ignition key. Do other consumers have power after switching off the key?

 

[gte619n]

Unless I hit the wiper button, everything works as expected. The wiper relay under the dash is disconnected, so I don't think it's part of my problem.

In the fault condition, everyone has power, including the ECU.

 

[Ohmess]

Check the load shedding relay

 

[gte619n]

Checked the load shedding relay, it appears to work as expected. On the bench, bridging the control pins creates continuity across the voltage pins. When I remove the voltage it closes as expected. I did notice that when I'm in the weird error condition, pushing the wiper stock makes the load shedding relay disconnect.

 

[Ohmess]

What else is wired to fuse 4 on your car?

 

[gte619n]

Well, that's got a bunch of stuff. Seems to be headlights, brake warning light, parking light (l and r), etc. Basically, everything that comes on when you turn the key to the on position.