96 850 - Lamp Failure Warning Light

sntee · Post by **sntee** » 21 May 2007, 02:00

After washing my car a couple of weeks ago, the Lamp Failure Warning Light came on.

I've checked all the relevant bulbs and everything is OK but the lamp won't go out.

Any ideas?

Rev · Post by **Rev** » 21 May 2007, 07:09

Have you checked your third brake lamp on the tail as well?

I had this light turned on, and it turned on every time I was on the brakes. Pretty cool, I didn't know this car had this.

zenmervolt · Post by **zenmervolt** » 21 May 2007, 09:28

The light functions by detecting increased resistance in the lighting circuits. Very rarely, if there is a flaky ground or other issue with the wiring that causes higher than normal resistance, the light can come on without a bulb being burnt out.

I say double-check the bulbs just to be sure and then start looking for a short somewhere.

sntee · Post by **sntee** » 21 May 2007, 09:29

That's the odd thing that I probably should've mentioned earlier.

All the brake lamps are fine but I have noticed the following......

I have the common problem with my ignition switch whereby it doesn't spring fully back into position 2 after I start the engine. I have to physically turn it back myself otherwise I lose the speedo, interior lights, headlamps, indicators, etc, etc.
However, I've noticed that when the ign is sitting in the limbo position, the bulb failure warning lamp only comes on when I apply the brakes.

This makes me think that the problem lies with the bulb monitoring circuit itself, rather than with any of the bulbs.

zenmervolt · Post by **zenmervolt** » 21 May 2007, 13:52

I say replace the ignition switch and see what happens there. You obviously need to do this anyway.

After that, if it's still a problem, you have a dodgy connection somewhere in the lighting wiring that is giving higher than normal resistance values and thereby triggering the light to come on.

bugeye58 · Post by **bugeye58** » 21 May 2007, 17:23

Check all of the contacts on the rear bulb holders. On my 850, and the 740 wagon, they sometimes make lousy contact and trip the bulb light.
Jeff