dash lights 1,2 & 4 are out on w124

[richard28]

I have this weird problem- on my 88 300CE, only three months old, only dash lights 1 (02 sensor), 3 (SRS) & 4 (ABS) don't work, meaning none of them come on for that brief moment when I start the car or with key on, engine off. The bulbs are good-I swapped them from another working dash. No other electrical issues- the OVP fuse is OK, the O2 reading, key on, engine off, is good & all other lights work fine. Car also runs fine, except for small miss I can live with & possible tranny shifting issues which I don't think relate to the dash lights. I'm particularly concerned I don't know if the ABS & SRS systems are working. Any & all thoughts would be appreciated. Thanks.
Rich

[Gilly]

Possibly our old friend the Overvoltage Protection Relay.
It's located behind the battery, behind the black cover. It has a flip-open clear plastic lid on top, and a red 10 amp fuse under the lid. Check that fuse. Even if the fuse is good, the relay itself may be bad.

Gilly

[richard28]

Thanks Gilly, but not it. I just swapped a good OVP, and no change. The lights stayed dark.

[richard28]

When I first pulled the instrument cluster I didn't want to bother disconnnecting the speedo cable, so I only checked bulbs 1(check engine) and 3(SRS). Last nite I squeezed my fingers in & pulled bulb 4 (ABS). To my chagrin I saw there was no bulb at all! When I inserted a bulb, there was light. Lesson to all-never assume anything (remember the first 3 letters of the word assume are there for a good reason). So, for good measure, I again swapped bulbs on lights 1 & 3, but current is not reaching the bulbs. So, Gilly & Board, my question, now more specific, is whether there is any relationship between the Check Engine & SRS lights on the dash; what/where should I check? Thanks.
Rich

[richard28]

Gillly?

[Gilly]

Is bulb #1 O2 SENSOR or Check engine? Have you checked the owners manual to see if this on is supposed to come on as a bulb test? The SRS also may come on only briefly. Can you check the bulbs with an ohmmeter? Or did you actually test the sockets for power? You'd need to have your voltmeter attached, THEN turn the key on as these usually only come on briefly after the key is turned.
Bulb 4, the ABS light, that one is fixed now?
I'm just afraid bulbs 1 and 3 could both be bad, as you pointed out, don't want to "ASSume".
Can you maybe swap the bulb out of the ABS socket (since you know it's good) and try it in 1 and 3, but again, remember you need to cycle the key off and on to get the bulb test.
One heads up is that if there were an airbag deplyment or some other SRS problem that a prior owner didn't want to fix, amybe the SRS control unit is disconnected.
With the O2 SENSOR or Check Engine light, that comes from the engine control unit, you may end up checking continuity back to the control unit, and if that's OK, boy oh boy, control unit time, that's why I'd be careful in finding out if that one even comes on as a bulb test, it's possible it doesn't.

Gilly

[richard28]

Gilly, Thanks for your thoughtful post. Bulb no 1 is check engine, which should be triggered buy a bad 02 sensor, right? Wouldn't it be easier to test #1 bub if I disconnected the 02 sensor under the passsenger mats, which would make the light stay lit full time if it was working?

[Gilly]

Richard:
I think that MAY work, I'm not really sure. I'd research if the light should come on as a bulb test, maybe you can just start a thread mentioning your cars year and model and ask if this light comes on as a bulb test or not on other cars.

The SRS I know is supposed to come on, so maybe it would be a good idea to research that one next.

Gilly

[richard28]

Thanks Gilly, I'll do that now that I just finished swapping out fuel distributor/air flow meter/fuel pressure regulator/idle control valve assembly on my 87 300e. This board gave me the confidence to attempt that, & it was pretty straightforward, except for reattaching two of the injector fittings especially the one above the hose from the idle control valve.