First, do you have an accurate wiring diagram? Use that to find out what
other "devices" are on that same circuit. Once you find them, test them to
see if they are working correctly. Is it just the rear turns, or the fronts
as well?
Next, with a volt meter or tester, put the brake lights on and see if you
are even getting voltage to the lamp socket. If you are getting voltage, how
much? You may need to do some more cleaning. Be sure that the sockets are
properly grounded and the ground is clean.
If you are not getting voltage, you need to go back to the supply for that
wire. You said the fuse was good. Did you do an electrical check or visual
check....are these american tube fuses or Lucas fuses? Laugh, you may, but
these cars were designed to use Lucas fuses and their blow point IS
different. For ex. a 35 amp Lucas has a blow point of 17 and a 50 blows at
25. Lucas fuse or not is really not an issue here, though.
At some point in the wiring, is the branch that takes electricity to those
brake lights. Have you tested the brake light switch (activated by the
brake pedal)? you should get a reading there. Have you tested the bulbs? The
filaments may look ok, but if that solder bump on the bottom is worn
down...no light.
The other things that I have done are to disconnect the battery and clean
out the fuse box (emery cloth and a good aerosol electrical cleaner on all
contacts). Second, was to replace a fuse box. On that car, a new fuse box
made a noticeable improvement on all circuits.
Compared to the complexity of the wiring for today's cars, our LBCs are
"tinkertoys". They may like to think they have us fooled now and then, but
we figure out their tricks soon enough.
Good luck
Valerie Stabenow, mga, tr4a, xk-e, tr6
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