I need help with a probem on a 1992 300SE W140 , yes its the first year of the W140 and it has a few bugs but I love the car. It seems at any time the right directional light will come on and stay on even if the ignition is off, this is a problem since it drains the battery. When its on, both the front and rear lights are on and the arrow directional on the dash, it comes and goes with no reason, is there a light control module or maybe a flasher unit??? Took it to 2 shops couldnt find anything wrong, but I dont really think they checked it. Any help would be appreciated or if you could reccomend a shop in the nort NJ area.

Are you certain that the headlamp switch is being turned to the off position? If you inadvertantly go beyond the off position it will illuminate the running lamps on the exterior (right side, left side) based on the position of the switch. I cannot recall if it would illuminate the turn indicator in the cluster, I would need to review the diagram more closely but I think it would.

Yes, I checked that,, its not the head light switch, that would illuminate the parking lights, not the directional.

I'll dig into the ETM and get back to you a little later, my immediate suspicion would be a combination relay OR a lamp failure control unit. Combination relays were a common failure for that era, at the moment I am unable to recall how the relay ties into the lighting.

Talk to you soon.

Thank you, any help would be appreciated

The way I see it, you have an issue with either the combination relay or the lamp failure control unit. The combination relay was problematic. Underneath the fuse box cover there is a section in the rear that houses several relays and control units. The unit closest to the fuses should be the combination relay. I would think that the next time the lights were in the on position try disconnecting this relay to see if the lights go out. If they do then I believe it is conclusive, order a new combi-relay.

If they do not go out try removing the control unit behind it, that should be the lamp failure unit.