> Can anyone tell me a good way to troubleshoot
I would start at the flasher unit (aka relay) on the firewall. Turn the
ignition on and use a voltmeter, DMM or test light to verify that you have
12v on both of the side tabs.
If neither side has 12v, then the fuse is blown or there is a wiring problem
somewhere between the flasher and the ignition switch. In that case, I
would move back to the fuse block and check there that there is 12v on all 5
terminals.
If there is 12v on one side of the flasher but not the other, most likely
the flasher is bad. You can temporarily connect a jumper between the two
side terminals for further testing, but with the jumper, the turn signals
will not flash, only light solid.
If you do find 12v on both sides of the flasher, then I would turn the
switch in the control head to one side or the other, and check again at the
flasher. If the power "went away", see above.
Then check the 3 smaller wires of the 4 that go into the subharness that
runs into the steering box (at the sleeves where they join with the rest of
the harness). Two of them should have 12v. If only one has 12v, there is a
problem with the switch in the control head, or the subharness inside the
steering column. If neither has 12v, there is a wiring problem somewhere
between there and the flasher unit.
Note that, if your car is LHS, the wire between the flasher and control head
pops out of the harness near the RH horn, and has a sleeve to another wire
in the harness that comes out near the LH horn (where it is attached to the
wire to the control head). If that RH sleeve is disconnected or broken
internally, that would keep the 12v from getting from the flasher to the
control head connection.
That should be enough to get you started. Report back with your findings.
One other point, the flasher (relay) will not work properly without both
turn signal bulbs connected to it. It should do something (eg flash very
slow or very fast, perhaps just light them solid) but some units may not
conduct at all. This is where the jumper at the flasher comes in handy, you
can get all the lights working properly and then try the flasher again.
Also worth noting, perhaps, that only the last 4000 or so TR3s had two brake
lights. Before TS18913, there was only a single brake light in the middle.
You wouldn't be the first to find that someone has tried to change that,
without really understanding what they were doing.
Randall
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