Hi All:

About twice during the past year and a half, my dash light out warning would come on. Each time I would just wiggle the passenger side tail light and it would begin working again, until yesterday. I wiggled it, tested the bulb and still it would not come on.

I got my multimeter and tested the voltage at the bulb socket. It fluctuated between 3.5 and 4.2 Volts. I tested it at the incoming wire connector, and it was about the same. I checked the resistance and it was only .03 as compared to a light that was working which was .02. I'm really not sure why, but I then went to retest the voltage at the incoming socket and it was 7.4 Volts. I then tested it at the bulb socket and it was 7.4 for a short time and then it went as high as 10 volts, but when I twisted the bulb in, it would not light, and the next time I tested the voltage it was back down to 3 and 4 volts.

I have checked the fuse and cleaned the fuse connectors, but the truth be known, I am really stumped! Can anyone give me some clues as to what is going on, where to check, etc.?

Thanks much, I really appreciate any advice you could give.

Thos 43

looks like a voltage drop somewhere, look for the next harness connector between socket and power source, also confirm your grounds. does putting in a new bulb help??, you may also try electrical contact cleaner on all related fuse buses and harness connections.

It could be the turn signal switch is failing. If the other side brake light works ok the turn signal switch is the most likely failing component.

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

Thanks Workerunit and Richart for your input. No, a new bulb makes no difference. I will check all the connectors, which I hope I'll find either under the back seat or on the firewall. I'll also test the turn signal switch, as the other side tail light works perfectly. Also, I just noticed my mislabeling this as brake light problem, when it is a tail light problem.

Thanks again. I'll post my findings.

Thos43

I had a similar problem with my 1993 400E. All the lights except one tail light was getting power. It had been an intermittent problem for a few years, but progressively got worse. I took apart the tail light assembly (pulled the metal out of the plastic) and used some fine sandpaper on the contacts thinking it was corrosion that was causing the problem. When I put it back together it worked. I don't know if it was just a bad contact that might have been reseated when I put it back together or whether it was corrosion. In any case, I never had to deal with it again.

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

I'm in the Emerydc8 camp. I would be stunned if the problem was somewhere other than in the taillamp assembly.
Don

If it's a taillight problem it isn't in the turn signal switch - that only applies to brake lights!

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

Thanks Emerydc8 and dpkreuze, I will take the metal center out of the plastic and clean. The only aspect that is dampening my hope of that being the cure is when I did a voltage check at the connector, the input voltage on all the pins was 12 volts + accept the tail light pin, which was 4 some odd volts at first then fluctuated up to a little over 10 volts, then back down to 4, but even if contact cleaning isn't the solution, it is never a waste of time.

Thanks again, I'll let you know the outcome.

Thos43

The voltage problem may be due to the bulb failure warning module in the fuse box. I incorrectly assumed the supply for the taillamp was the same for the side marker. you could supply the taillamp with the circuit for the side marker (jumper) but the bulb failure lite would illuminate.

I had this problem on a 93 and some of the contacts had to be re-soldered. Common issue

Hi All, thanks for your input. Unfortunately it was not a contact problem. I cleaned all the grounding points and the power points as well as re soldered the wires, and it still doesn't work. I am assuming it is in the warning light module, so for now, I think I'll just jump it from the side light until I have time to replace the warning module; that is unless someone knows how to test those things?

Thanks again, you've all been a great help.

Thos43

Sorry to hear that. Jumping it would probably be cheaper than replacing the warning lamp module. I don't even know where it's located. It sounds expensive.

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles