Dash Lights Dead and OBC light dead

[Vanilla Gorilla]

I am having a crazy problem with my 89 325I. When I pull out the headlight switch to turn the lights on at night the OBC light shuts off but I can still see the time, date, etc... so it isn't losing power competely.
If I put some form of light into the little blue laser eye that tells when its night time out the OBC light will come back on.

I have replaced the headlight switch and it fixed the OBC issue but not the dash lights. Then after a week the OBC light started turning off again when I turned on the lights.

I have a system in the car and it has never had any problems before. Another odd thing is that the stock fader switch still lights up. It isn't hooked up to the head unit it is only still in the dash for the purpose of filling the hole. I guess the reason it lights up is because it isn't hooked up to any of the problem wires.

My big issue is that I don't have any dash lights it is a pain. I have checked connections and grounds and haven't been able to find anything. Has anyone ever had a problem like this before. Any input is greatly appreciated.

Any ideas on what I could check.


Also all fuses are good

[jht3]

did you replace the headlight switch with a BRAND NEW or known working switch?

me thinks you have a blown rheostat in the headlight switch. put a jumper wire across the rheostat and you should have full illumination

[808BMW]

did you replace the headlight switch with a BRAND NEW or known working switch?

me thinks you have a blown rheostat in the headlight switch. put a jumper wire across the rheostat and you should have full illumination

What is the rheostat? I've heard of this but don't know what to do, my dash lights have been out for months :(

[browntown]

This might be the stupidest post I've made, but ummm, I've never looked, but I assume there is a dimmer? is it just turned all the way down? turn it up.

[Vanilla Gorilla]

Thanks very much for answering my post but I have also never heard of this part. The switch was not brand new it was used. Could you explain how to locate a blown rheostat in the headlight switch. Thanks

[NC325iC]

try twisting the headlight switch to the right, thats the dimmer/rheostat

[DrMcDave]

jht3 is right you need a new headlight switch. The rheostat acts as a fuse in this instance. i did the same thing to my car when replacing my dash, plugged the AC switch into the hazard switch and my lights stopped working (it can prob happen other ways).

[smithy318i]

The way to test if the dimmer is faulty is to remove the rear ashtray and access the light bulb below it. Then connect the brown wire directly to the metal of the bodywork. If the dash lights come on you know the dimmer is faulty.

HTH.

[Vanilla Gorilla]

Thanks I'll try it later today and let you guys know what happens.

[skool]

hey guys, I'm having the exact same problems on my car as well.
could it be that the lights in the dash are just blown and need to be replaced?
because when I use the dimmer, the instrument panel lights, rear ashtray, hazard, and defrost lights dim.
any ideas what might be causing this?

[jht3]

a rheostat is a dimmer. in the e30, the rheostat is built into the light switch. by twisting the knob, you are changing the resistance via a potentiometer.

either buy a new light switch or do what i did: insert a short length of wire into the back of pins 6 (brown/white wire) and 2 (brown) on the light switch. this bypasses the blown rheotsat.

[browntown]

rheostat=most commonly used for high current pot
potentiometer=variable resistance knob like a dimmer or a volume knob.

The problem with pots, is when they hang out in one position a long time corrosion and wear will make them not so useful. Just like the throttle body pot (TPS) in my volvo, the contacts were worn down around half throttle, and my ecu went bonkers about 3k then returned to normal at wot and idle. Replace it. Post in WTB.