1986 300SDL...whats this little glitch!?
 

I have a 1986 300SDL and the other day I started it up in the evening and the burned out bulb warning light came on (the little amber light next to the ABS light). I also got a little dummy buzz for about 5 seconds then it stopped but the light stayed on. I figured i had a burned out bulb and Id check it at home. There were no burned out bulbs...everything was working, reverse, turning brake, fog, everything. I started it back up again and it didnt happen this time. I let it go, then, this morning...I started it up and threw it into reverse and the buzzer came on for 2 seconds then turned off...this time, no little dash warning light. It doesnt do it often...it just started. What does it sound like, or is there a known glitch in this car?

I have had some flickering of the bulb indicator but not the buzz. The two issues I had were once with the center brake light (forgot about it and bulb was burned out) and another with some cheapo China bulbs.

Have the 'burnt out intermittent indicator' issue right now. It is one of the tag lights. The gasket was not properly installed, allowing the inside to get dirty, and although I've cleaned it, it still does not work 100%

Doesn't the buzzer have something to do with the seat belts ???

On my SDL, if I have the set belts buckled first I don't get the buzz. If not, it buzzes for about 5 seconds. I use it to time the pre-glow. Then I buckle up an start it.

Intermittent "bulb Out" lite is usually an indication that one bulb is not making good contact and will remedy itself when you go over a bump. Could be a filament or just a bad contact.

Mine happened with the little license plate lites. Always over-looked because they are hard to see in the daytime.

As to why in reverse....haven't got a clue unless you have an intermittent problem with the seat belt latch wiring.

A reverse bulb isn't making good contact?

There isn't a buzz to accompany the bulb warning indicator but the warning systems probably share a fuse or ground. Low voltage will usually trigger false warnings.

When electricals start to go goofy, it's a reminder to replace ALL the fuses if you haven't done so in the last 10 years. Also check the condition of the alternator brushes (disconnect battery, remove regulator held on by 2 philips head screws on the back of the alternator). Low system voltage will typically trigger the ABS light then the accessories will drop (cruise control, power windows, etc.).

Sixto
87 300D

When I've had that problem and there wasn't anything obvious, I found that it was either the tag light or one of the brake lights. Of course, if the warning light only comes on first when you hit the brakes, that tells you. But I'd check the tag light on the rear, which isn't necessarily obvious. Whenever I have gotten that warning light, I've always eventually found the culprit.