1993 300TE M104 wagon, no power to right rear taillight

[JensenHealey]

I am trying to finish up the last few jobs on my 1993 300TE and I discovered the other day that I have no power to the right rear taillight bulb socket.
The turn signal and brake lights in that same lamp housing work fine and the taillight on the left side of the car works fine.
This evening I pulled the fuse out of the fuse box that was labeled as going to the right rear taillight and carefully cleaned both ends of the fuse and then checked to see if I was getting power through to the ends of the fuse.
I was getting power through the fuse but I still do not have any power at the right rear lamp housing.
I have also removed the cover from where the plug on the end of the pigtail plugs into the socket on the wiring harness and I do not have any power going to the pin on the socket that should transmit power to the bulb position for the taillight.

Anyone have any suggestions as to where else I could look to see where the problem might lie?

 

[optimusprime]

J H I would remove the light cluster from the rear wing , you might see a problem with the cluster .. Then from there work back to the conection plugs .. If it is still untraceable you could piggy back a live wire from the other light . Might sound silly but have you the right bulb in,, and in the right way .Some are double element bulbs. Also try the bulb thats not working in the other light on the laft hand side .

 

[tjamesbo]

This can be caused by a failure in the Bulb failure relay box I had this on a front sidelight I had no positive ffeed I replaced the relay with one from my other 124 and bingo it solved it so I ordred another relay The relay is the long box at the rear of the Fusebox
I'll try to find my original postings

 

[JensenHealey]

Thank you, I am looking at the W124 wiring diagram now for the exterior lights and I see an "Exterior Lamp Failure Monitoring Unit" that sits between the power flowing from fuse 3 and the right and left tail lamp bulb holder.
Any information you can provide would be most helpful.

 

[Habil]

the exterior lamp failure unit is behind the fuses. its a long black relay. to access it remove the fusebox lid, undo the 5-6 screws holding the plastic cover behind the fuses. its the relay on the right.

 

[tjamesbo]

You must eliminate the other causes before trying this ie Bulb / Cluster / Poor Earth connection if there is no or no 12V positive under load then it could be the relay unit

 

[JensenHealey]

I removed the exterior lamp failure module and took it to a friend who is an electronics expert. He found two places on the circuit boards that looked suspect. He re-flowed those two spots and I reinstalled the module back into the car. That fixed the problem and I now have working taillights on both sides of the car.

 

[alabbasi]

Funny,I was going to suggest the bulb failure module. It just literally happened to me on my R129. Same fix.