No Low Beams on '92 300SL
 

I looked at a 300SL today that has a problem: no low beams. The headlamps are new. The high beams work fine. And when the lights are switched on, all the other lights come on. Any ideas would be appreciated.

I've replaced a few combi-switches on these lately. This is the turn signal switch assembly, which also controls the wipers and the high/low beam control. The other possible suspect is the exterior lamp control unit. This all assumes the bulbs are OK and the grounds are good.

Gilly

Thanks for the response, Dan. Somebody (a mechanic?) told the owner that it could be a relay that is under the main fuse box. Is this the exterior lamp control unit you mention?

The relay for the exterior lights is at the far back of the main fuse box, have to take off a few screws to get to it. This controls all the outputs to the exterior lamps except the center stoplamp, which is hardwired from the stop lamp switch. i believe it would take a double failure of the relay to cause this to happen (both lowbeams out). I would tend to stick with the combi-switch diagnosis.

Gilly

ps it's not an extremely expensive part to replace or hard to do. I think the relay costs alot more for the part, but of course is easier to install. I think the combi switch is in the $100-$200 range and can be done in 1 or 2 hours

The HIGH beams have their own fuses & so does the LOW beam lights. When the LOW beam lights are on do the low beam fuses power up?? IF not the the combination switch is the problem. IF the fuses do power up then the lamp monitor relay would be at fault!

Bad Combo Switch
 

No power to the low beam fuses with the light switch on. Thanks fellas.