Dash lights

[Sanchez]

Hi peeps.

My dash light work when ignition off and lights switched on but when I turn the ignition on and start the car the dash light fail.

Any ideas?

[Sanchez]

Anyone help shed some light on this please?

[Sanchez]

Still can't find the solution. Any fuses other than the fuse box?

[Brianmoooore]

The only fuse on an E30 that is not in the fusebox is one associated with the heater electric valve, and although I haven't much idea yet as to what your problem might be, I'm fairly confident it's nothing to do with that fuse.
Pull out the rear ashtray, remove the bulb holder from its clip, take a piece of wire, connect one end of it to a good body earth, start the car, turn the lights on, and touch the free end of your wire to to the terminal on the bulb holder that has a brown/white wire.
Do the dash lights come on? Do you get a large spark?

[Sanchez]

This shall be tested in the morning. Ta.

[Sanchez]

No dash lights and no spark when brown white earthed.

[Brianmoooore]

This is a weird one!
Can you list the exact lights that work with the ignition off and fail when the ignition is on, or is it they fail when the engine is running?

[Sanchez]

Due to my working hours this may drag on but,

Window switches illuminated when door open.

Dash lights work normally when light switched pulled and key not in ignition.(obc, speedo, headlight switch, havac bulbs and switches illuminate(fan speed bulb dead, has been a while)).

When key turned to position where service lights on, dash lights go out, service lights stay illuminated until engine started.


I have a day off on Thursday and will be swapping the instrument cluster out to a spare I have but its not a regular black face one. It came in a old 318is I had, white dials that can glow blue or green. Has BMW logos and ///M stamp but not sure if genuine.

We shall see and I will report back.

[Brianmoooore]

Check your number plate lights. Do they do the same thing?

[Sanchez]

All external lights work as they should.

[Brianmoooore]

Stranger and stranger! The number plate lights are on exactly the same circuit as the dash lights, hard wired together, so it's difficult to see how the dash lights could not work while the number plate lights do, unless your wiring has been considerably modified.
The problem you describe could occur with the lights controlled by the rotary dimmer if ignition switched power had somehow shorted to the brown/white dimmer wire, but my first test eliminated this possibility, if you are sure you performed it properly.
Does the rotary dimmer work as it should when the lights are working?
You said above that the headlight switch illumination is included in this strange behaviour. Are you sure? It's not part of the main dash light circuit, and is independent of the lighting switch completely, only lighting when the ignition switch is on.

[Sanchez]

I've noticed the headlight switch and headlight level adjuster both stay illuminated. Difficult to tell in daylight but saw it last night.

I have a spare headlight switch so this can be swapped next. I've just swap the cluster and no change.

12 hours shift ahead now.

[Brianmoooore]

Does the rotary dimmer work as it should when the lights are working?

Don't start swapping random things around. It inevitably causes more problems than it causes, and often gives the worst possible outcome. - a 'cure', without knowing what the problem was, which then turns into an intermittent fault.
Analyse things as they are, determine the exact problem, and then replace or repair as required.

[Sanchez]

With swapping the headlight switch, everything works as normal.

I understand what your saying about swapping items over, but if the switch is at fault why not swap it for the working one.

I might swap the switch into my friends e30 see what that does.

[Brianmoooore]

With swapping the headlight switch, everything works as normal.

Doesn't explain how the number plate lights were working when the cluster lights weren't. The same section of the headlamp switch feeds both.

[Sanchez]

Strange, I'm not great with car electrics but I'm always happy to learn more and always chuffed when I fix it.

Will see how's things progress.

I thank you very much for your time and help.