1990 740GL, electrical strangeness

On the inside of each wing (on my UK spec 740, at least) is a bunch of earth (ground) terminals. I'd start by checking all of them as 740s seem to have real problems with earthing. Check the engine earth strap too (attached to the bulkhead). It seems that it was made a little too short - mine had snapped.

Si

Sounds good, I'll check. Er, what's the USA word for what is called a "wing" in the UK?

Fender. Boot is Trunk, Bonnet is Hood, estate is wagon, saloon is sedan, Sills are Rocker Panels, manifolds are headers. I may be wrong about Fender, but it is the word that sprang to mind.

All the best, Peter.

Fender

Heh! Fenders, as others have said. I imagine that our continued use of the word "wing" originated from early cars where the fenders did look a little like wings...

Mac,

This sounds great, I will definitely make this a project.

Regarding my 740, I checked the grounding harnesses inside each fender. There were two on the passenger side, and one on the driver's side. They did not look corroded and were properly affixed. I didn't see any wires that appeared to have come unclipped from either fender ground.

I did find one more clue to my problem. I noticed that my driver's side headlight is extremely dim. When I turn on the left turn signal, both the driver's side headlight and the flasher blink weakly. The passenger side light is fine.

So right now the turn signals are work> I have just gone through the same deal with my 90 wagon.

Whenever you have dim lights, and switches from one device affecting another, then I always suspect grounds. Keep in mind the problem can be anywhere on the ground wire from the connection at the device to the connection on the body.

Mike F wrote: > Whenever you have dim lights, and switches from one device affecting

Ok, then it's pretty certain I've got a grounding issue. If I've already looked in the obvious places and don't see bad connection, is there a way to locate a bad ground, like a tool of some kind?

JR

One tool that is necessary would be a voltmeter. Put one lead on the negative battery terminal. Measure the voltage at the ground wire at the headlight. It should be close to zero, I'd say maximum about 0.3 V. Another tool that would be very helpful is a wiring diagrams manual, so you know which colour wires are supposed to do what. Because your wipers are turning on, I ask the question, what are your windshield washers doing during all this?

Washers are inactive -- it seems to be affecting only the wiper motor.

What turns the wipers on other than the wiper switch? The washer pump. Energizing the washer pump fires up the wiper motor, so if your headlight is being grounded through the washer pump, then the wiper relay will be receiving a signal down that wire, and will turn the wipers on. Try disconnecting the wires at the washer pump.

Rather than just rely on my visual inspection, I decided to follow the advice here and disconnect/clean/reconnect the ground wires inside the fenders. Vallah! Problem gone.

I still don't really understand why my #8 fuse (turn signals) was blowing immediatly upon insertion, but everything's back to normal now.

Thanks to all who responded!