1990 300SL Brake Lights inop...

[bikebitzofvt]

Hi all,

I'm looking for help with my brake lights on my 1990 300SL R129 - they simply don't work. I figured if I post on the "big 3" MB forums (here, MBworld & benzworld) I might get the help I'm after.


So the only problem I haven't been able to sort thus far is the brake lights quit working. The warning lamp came on and got brighter when I stepped on the brakes. I first tested the stop lamp switch switch, shows .3 ohms or open when depressed or released depending on the circuit or 1/2 of the switch tested - appears good. With the key off or on it is missing the 12v supply to the switch. The fuse is good. I even cleaned the connections in the whole box just to be safe. I have the star ETM but can't get the diagrams to open. Does anyone have the wiring diagram available for the exterior light circuit? Trying to back trace the power to the switch and determine which relay is involved.


Any help or input would be greatly appreciated!
Thanks,
Tom Merlau aka bikebitzofvt

P.S. Also looking for a overhead console housing and a side skirt jack point plug and new roller doors for the cassette tape/lighter box for reasonable money... also need a couple of key blanks so I can cut some spares...

[bikebitzofvt]

Well I found a crispy circuit inside the light monitor module (Part Number 1295420132) I was able to disassemble the module, remove the burnt resistor, source a new one at an electronics supply shop for $3.00 and repair the solder joints. I just wish I had a reason for the failure, a thorough inspection of the related wiring didn't show a cause; I did remove a hacked hidden radar detector install from behind the dash, the power wire was chafed but it never popped a fuse??

[tecqboy]

It is possible that someone replaced the lamps with bulbs which draw higher current than the originals. That would over time cook the resistor.

[Softball60]

My brake warning light goes on everytime I restart the car as soon as I touch the brake pedal. Brake lights work but can't figure why the warning light goes on everytime.

Any suggestions??

Thanks