Incorrect Factory Wiring in Doome Light

As a result of a bad switch in my dome light I ordered a used one (in which I had to transplant one switch from my original unit.) During installation I discovered that the factory connector had been wired incorrectly. There are 5 leads into a six pin connector, which connects to the 4 pin connector on the assembly, so rather than starting on the first pin the factory pin from the car had been started on the second pin which left the background lighting unpowered FOR 13 YEARS!!
The wiring diagram in the WS Manual is correct so if you suffer this problem check the factory wiring. It could be wrong! After rewiring the pins everything worked perfectly.

Virgil

 

My symptoms were the same and neither spotlight nor dome light, when activated through switch, worked at all. You need only have a continuity tester and maybe a couple of jumper cables, and a ground tester. The whole back of the switch is literally a wiring diagram so it is easy to follow.

1. Remove dome light assembly and disconnect the connector to the factory wiring and separate the two pieces.
2. On the lighting unit piece locate the two solder points directly above each push button switch, you'll see where
they push through the "diagram" of metal circuits.
3. Put continuity tester pins on the two soldered points for each switch (separately
obviously) and actuate the switch under whichever pins you have connected. If the
switch engages properly the continuity will exist/not exist as you push the switch in
and out. If it doesn't work you need a new unit unless you are daring!
4. If you have a ground tester you can check the factory wiring. You should have a
yellow/red wire that is hot only when your light switch is on on the light switch on the
turn signal stalk for background wiring. There is a black (ground), and a blue and white which I believe are
always hot (at least one is.) THERE IS ALSO A BLACK/ORANGE STRIPE WHICH
CONNECTS TO NOTHING! Mine DID and that was the problem for me.

That's really about it. Transplanting a switch is not easy and requires a lot of imagination and some skill in various task. Most people should not try it. For me after PERSONALLY restoring my 1955 Mercedes Gullwing it is no big deal. JB Weld is a savior!

Hope this makes sense and helps!
Virgil

 

Not really much to see but I'll see what I can do. If you follow the above instructions it will become obvious. The wiring diagrams are tough but it is all exposed on the back of the lighting portion of the assembly as metal strips and very simple.

Virgil
1999 F1 Modena