91SL light monitor driving me nuts
 

On my 91 SL, the illumination warning light keeps coming on. The light I am talking about is the one intended to warn of a burned bulb. The right stop light has an intermittent connection problem. I have replaced the bulb, I tried bending the spring to make better contact, finally I replaced the entire tailight assembly, but still that #@$% warning light comes on when I brake while going over a bump. The stop light always works again after a few seconds, but the light stays on.

Now, I obviously have an intermittant bad connection somewhere, but where? I would like to fix the stop light, but I will happily settle for disabling that @#$% dash warning light. Can I just pull a relay? Will any other system be affected?

Thanks,
Roger

When replacing the bulb, I assume you used the correct wattage?

Also, the replacement bulb should have the nickel-plated housing...Osram, Philips, and Sylvania are those types. Stay CLEAR from the gold anodized units. They send a different resistance than the nickel ones, and will send an incorrect signal to the light indicator system.

Also check the condition of other bulbs in the system. Other bulbs that are on their way to failure will have filaments that would be sensitive to vibration (i.e. bumps) prior to total burnout. Check the other stop light AND the third brake light...

I replaced the entire tail light assembly two weeks ago with a new factory unit. It still has the factory bulbs, so I am inclined to suspect the trouble lies elsewhere.

To be honest, I really don't like this monitor system and would rather just disable it. Does anyone know if this is possible?

You can pull the instrument cluster and remove the bulb. There are special tools for removing the cluster available from the dealer, though you could probably get by with something fashioned on your own.

Update-

I think the problem is with the socket that plugs into the tail light assembly. Every time it acts up, I push this socket firmly into place and it seems to be okay for a week or so.

Thanks for the replies

Roger

One thing that is definitely NOT your problem is the center stoplight assembly, as it is NOT monitored. All of these other circuits are actually provided by the lamp control module, which is how the monitoring is provided. The center stop lamp assembly is fed directly by the brake switch, not through the module.
Happy hunting!

Gilly

me too on my 86sl
 

I have the exact same problem on my 86 sl. My local MB mechanic has checked the wiring. He said that he thinks it might be the light monitor relay. Does this seem like it could be the culprit?

Again the problem is an intermittant loss of power to one or the other brake lights and to the drivers side high beam(bulbs are fine). The hi beam works much of the time..but as soon as the warning light on my dash is illuminated you can bet the brake or the hi beam is what's out.

Thanks for you help!

How odd, I have the exact same thing going on in my 91 500SL. It seems the right rear light will go out intermittetnly and the dash light will light up. I havent gotten into it yet, to see if there are any loose connections.

That is odd..what do you think Gilly?

I think that my problem was the plug that connects to the taillight assembly. I pushed that plug in as hard as I could and the warning light has stayed off for almost a month now, and still counting.

Roger