Hi again, (this is lengthy, sorry; bottom line: wiring harness error by British
Wiring)
Guess who stupidly made the following statement ...."... Installed a new
wiper/washer switch to go along with the new wiring harness so it's unlikely
that it's a faulty electrical configuration..."? Yep, guilty as charged. I
spotted the problem yesterday and tried a fix but the attempted fix was with an
erroneous assumption.
If you missed the first installment ... the problem was that my wiper motor
would not shut off after installing a new wiring harness and a new wiper
switch. The wipers didn't work at all when I first got the car, a '77MGB. I
removed the wiper motor (a real pain in the neck operation since that's where
the a/c heat exchanger is located), disassembled the wiper motor and gearbox to
look for an obvious fault. None showed up. Remembered my Lucas Trouble
Shooting Guide and ran the tests on the wiper system. Passed with flying
colors. Spent much time studying the manuals, measuring voltages, etc.. Finally
spotted a pair of wires that didn't match the wiring diagram color code. I
mistakenly tried to correct that condition by swapping the wires at their 'other
end', i.e., at the connector where the wiper switch plugs into the harness.
That 'fix' didn't work.
Down in the basement I still had the old wiring harness. Removed the wiper
motor again, along with the new wiper switch and reconfigured the setup on the
bench. (That part of the wiring hadn't been screwed up bu the PO's electrically
challenged mechanic.) It worked fine once I figured out where to connect up the
battery. It was while trying to connect up the battery and avoid losing all of
the smoke that was still in wires that I realized where the problem was ... not
all green wires or grounds are where you think they are. The wires that were
reversed at the motor plug on the new wiring harness are a green wire and a
red/light green wire. These same wire colors appear at the wiper switch, but
the green wire at the wiper switch is not the other end of the green wire at the
motor plug. When I tried to swap them at the harness it didn't work because
that's not where the motor plug gets its 12v from.
As we all know by now, the green wires are the source of 12v through a fuse when
the ignition switch is turned on. The wiper motor uses the 12v from the green
wire as part of the auto stop system. The lack of 12v on pin 4 of the motor
plug caused the motor to run continuously since its presence on pin 5 connects
it directly to one of the brushes in the motor.
Solution: swap the wires on pins 4 & 5 of the motor connector. Ed Kaler from
Just Brits is telling British Wiring about this. I don't know if this was just
a goof in assembling my harness or an mistake in their layout. As frustrating
as losing a day trying to solve it is the cost of the new switch that I bought
when I first spotted it.
I'll tell you about my other connector disassembling tool for the motor plug in
another post.
Bud Krueger
52TD
77MGB
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