740 Brake Lights

Lost the brake lights on our '86 740. Stoplight switch at pedal is OK, has
almost 13 volts. But nothing at the rear; taillights are OK. Any
thoughts?

 

Open up the bulb failure sensor, it's the red can in the fuse box. You'll
find cracked solder joints on the circuit boards inside it. Reflow those
with some fresh solder and plug it back in, should be good to go.

 

Thanks. Looking at the wiring diagram, I thought that could be the problem.
The audio equalizer is above the plug-ins, so it's crowded. But I have
today's work cut out <vbg>.

J Corey
'86 740
400K miles -- all mine!

 

I pulled the red can and opened it up. Could find no breaks on the circuit
board, but there was a bit of corrosion. leaned it up, but didn't help, so
I jumped from the brake light switch to the brake light assembly. It got
the lights working. Now the strange part. When I removed the temporary
jumper to run it "properly", the lights began to work normally. But then
they crumped again. So I made the jumper semi-permanent, until I can get
to a junk yard.

Damn. The car only 400k miles and it's already falling apart.

J Corey
'86 740
400K miles -- all mine!