Maddening 'bulb out' problem
 

My 1988 300E sat in the garage for about 5 years. I finally got the fuel system cleaned out and got it restarted and everything seems fine except the 'bulb out' indicator in the dash was on as soon as the car was started and the ABS and SRS lights were lit. I knew the front driver's ABS sensor had its cable cut and I replaced it which put that light out and the SRS went out after driving 60-70 miles. At this point all the bulbs worked but the 'bulb out' indicator was still on as soon as the car started. I resoldered the relay (126 542 01 32) and everything worked but the driver's brake light. I got another relay from the junkyard and then had no brake lights, backup lights, or side markers (either side). About a week's worth of parts, and still no brakes, side markers, or backup lights from any of three relays. Somewhere in here I replaced all the fuses with brass ones.

All the rear lights work properly if jumped from the battery to the appropriate pin on the 10-pole connector under the relay. All the correct bulbs at the connector match the schematic. Even so, I cleaned up the ground contacts in the trunk with sandpaper and re-connected. There is now a brand new Mercedes headlight switch installed. I have about 13.4 volts on pins 8 and 16 on the 16 pole to the relay when the light switch is on. I have about 13.4 volts on pin 15 to the relay when the brake pedal is depressed. I did notice that I have about 7.4 volts when the pedal is not depressed. However, the anti-theft circuitry connects with the circuit just before this point so I don't know if this is normal or not. I did replace the rear antenna with an aftermarket Hirschmann before all this started but there are still no rear stop, reverse, or side lights with antenna either up or down. Both tail lights and all turn signals work properly.

Could I have three bad lamp control relays, should I try a stop light switch, or is there something else I have overlooked? Not sure where to go next.

It's possible. I know that in RWD Volvos, the lamp supervision relay is a known point of failure.

Every mercedes I've owned except the 300D has had a phantom bulb-out indicator at some point...I just live with it

Will, I wish that were an option now. After trying to fix it, now I have no brake lights (or side, license, or reverse). I disconnected the anti-theft system under the passenger carpet, pulled the brake light cable, and disconnected power and ground to the aftermarket Hirschmann and still no lights. I gave up and ordered a new lamp relay. Really can't see anything else it could be.

An update; I forgot the ABS input connected to the brake light circuit prior to the lamp relay so tonight I disconnected the ABS controller and tried it out. Same lights still out, but I did notice that, although the bulb out indicator is still on, the ABS warning did not light and it had been lit when the sensor cable was cut (until a few weeks ago). Also, the car ran like crap with the ABS controller disconnected. Don't know if it is pertinent; I am grasping at straws and was also notified that the new brake light switch and lamp relay did not leave the warehouse today. If it is not one of those, the last thing left is a bad common ground with either the lamp relay or headlight switch and so far I have been unsuccessful at identifying where the lamp relay grounds. Has anyone dug this far into to it?

Hey Nashville! Me too!
Wow, you seem to have covered everything.
Normally I'd bet on a ground at the bulb holder (brake lamp). My W210 ('96) had a similar problem (ABS/ECS + DEFECTIVE LAMP, whatever) I sanded my taillight contacts, too, then I removed the whole assembly and could see that the metal "runner" carrying the ground had overheated and melted the pin holding it on so it barely touched the lampholder contact! I bent the "runner" out and fixed that one. Shortly after that the dashboard lightshow came back; turned out the 3rd brake light had a contact that had arc'd away - not anywhere easy to find mind you, but where the housing's contacts slide into the assembly mounting slots!
One other time (no ABS warning though), it turned out one front side marker's filament had broken then reattached shorter, making it brighter! In your spare time you may want to "ohm out" all the bubs (hillbilly for bulbs).
Good luck, if it doesn't work out we can run head-on into each other fer the 'shurance!! (KIDDING- Ilove my car - and my karma).
-Tom

Don't tempt me with the head-on idea (just kidding; already too far in). I thought I had it. I read in another post where someone (I think MBDoc) posted where the ABS grounds were. I shined up the ones on the strut tower, and started looking for the ground strap for the ABS pump. I discovered that the nut which secures the strap was missing and the connector was barely hanging on the terminal. I cleaned it up and hit Home Depot up for a 5mm nut and still no brake lights.

To be honest, I gave up after cleaning the other end of that ground strap last night and drove it up to an indie in Lakewood today. I am sure I would eventually find the problem but Mom wants me to bring the car down this weekend so I can spend some time with dad on Father's day. At the rate things have gone, I am not so confident I can find it that soon.

3:50 AM? Goin' fishing?
Yeah, the ground fix would sure seem to be the winner. I wonder if it grounded through a circuit it shouldn't have and fried something?
Just curious, did you re-connect everything or is the ABS still d/c'd?
Also, I blew 2 fuses in the course of my last ABS repair, (completely unaware of when I did it - no "oh crap" sparks) so don't forget to re-check the obvious!
Let me know when the shop does the $100 fuse replacement for ya! (I hope not)

Did you take it to the Ferrari guy in Hermitage? I've heard they are good, and honest. Don't know the name of the shop off the top o'my head.
Lastly, where the hell did you find a junkyard with MBs? Not local is it?(I won't tell anybody) I need a trans for the wife's W210 w/M104 (guess it's a 722.3, not certain). My brother lives in LA and he's a porsche guy; he gets some sick Porsche deals in the pull-a-part there and says the places are full of W210 cars! I hate LA!
-Tom

Almost local; its Gray's in Lavergne. Don't know if he has any W210s but he has a few W124s. You turn off Murfreesboro Rd across from the airport just north of Sam Ridley. I took the car to Dan in Lakewood. I tried the Ferrari guy once and he was backed up for the next three days. I usually go to ******** downtown, but Dan is supposed to have a good nose for electrical gremlins and I didn't have to fight downtown traffic.