I found the problem with my '70 TR6 stoplights. They were working
normally if the parking lights were off, but if the parking lights were on
the left rear parking (and stop) lights would turn _off_ when you hit the
brakes.
A bit of thinking led to the conclusion that the brake and taillights
on the left rear must be grounding through the right rear lights. If you
had both on, both were at 12V (well actually 10.5V) and neither lights. This
conclusion was correct.
I checked the grounding of the socket. The reflector edge was clean,
the reflector was well-grounded, the clips were tight and clean. Hmmm. So
I measured resistance between the lamp body-contact and clip. Infinite. Aha!
The design of the bulb-holders on a TR6 is ludicrous! Nothing firmly
attaches the clip and the grounding contact for the bulb! It counts on
the fact that the metal happens to get pushed together in manufacture, I guess.
Pulling and pushing would cause some (poor) contact, but it wouldn't hold.
The solution was a piece of picture wire run through a clip and down along the
bulb.
I still don't know why the rear lamps see 10.5V. Resistance between
the rear body and the battery cable is .5 Ohms. And I still don't know why
the left turn signals only work with the engine running, but I'll track it
down.
I'm also trying to figure out why the hazard flashers don't work.
The switch doesn't seem to do anything: the turn signals still work (they
should be disconnected), the hazard relay sees no voltage. I looked (as best
you can) at the hazard switch (right above the steering column), and all
the wires seem to be connected to it. Is total lack of action a common failure
mode for those switches? (This is the early rocker-style switch.) The hazard
flasher may be dead, but that shouldn't stop the lights from coming on.
Randell Jesup
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