Electrical Question.

[Jonny weggie]

I'm going to start soon checking my wiring for O/S side lights [front and back] as well as dash lights which seem to be on the same circuit.They will not blow if sitting still but as soon as i drive away they will. If anyone has come across this problem and has an idea where to start checking,please let me know. PS -- CAR 350i. [89]. Before i start ripping the wiring loom out. THANKS ...

[jeff m]

That's a weird one.
I would check your alternator output before ripping stuff out.

[leorest]

Can't answer your question directly but I know there is something strange with the design of the wiring as when I removed the lighting fuses the near side tail light still worked. I've never had the time to investigate it further.
I'm sure Wedg1e would be able to offer some insight on this one but I haven't seen him posting recently. Rumour mill is that he has lost two wheels!

[djc1001]

A lot of the weird electric antics on the Wedges come back to earth and connection problems.
Glowing lights even when the fuse is removed is probably an earth problem.
As prev response check alt. voltage and then connections and all earths - put some direct temp earths in if necessary.

Best of luck
David

[Grady]

I had a weird side/running light problem (half didn't work) and was convinced that - under the wrapping - the harness came together around the rear license light. But turned out not to be true. 2 separate circuits, one for each side.

If it's only blowing one fuse, I'd guess a specific short downstream of the fuse box. I'd try "wiggling" the car, revving the engine & alternator, slamming doors and if the dash light are part of the problem turning the steering wheel. After that I'd guess it's a bad fixture.

Mine is a '86 280i if it matters.

Edited by Grady on Wednesday 13th August 22:57

[jmorgan]

Personally I would get a diagram (stop sniggering up the back!) and scope the issue out. A recent oddy with mine was the switch. The switch can be dismantled and cleaned which cured it. But that was after the chattering relay. And that was after the dodgy connector on the back of the head light etc etc.

But, what I did find on the 400, was the front lights were fed to the passenger side then across to the drivers side. So for my problem if the passenger side was working then there were volts getting that far, only the cross car cabling and connectors to check. Oh, and the earths (on the 400) are on the passenger side suspension part of the chassis in the engine bay.

Probably find the the 350 is different to the 400 though

ETA, volt meter extremely handy in this.

Edited by jmorgan on Wednesday 13th August 23:10

[TVR 3X]

A Voltmeter is great for many electrical problems - but if checking lighting etc it is difficult to beat an ordinary sidelight bulb (5W) on leads.

Voltmeters have quite a large internal resistance so they don't take much current and can mislead (dodgy earth etc.) but a bulb half glowing can show up a high resistance connector and all sorts of other problems, it takes sufficient current to show these things up.

Probably best to have both.

Russ

[erik280i]

You can replace the fuse by a 50W 12V bulb. Then if there is a short circuit the lamp will burn. Makes it easier to find the problem.

[Jonny weggie]

Thank you, will try it out.

[jmorgan]

Must admit I have forgotten the use of the bulb and wire when the multimeter appeared in my garage.