Yes, I am saying that the circuit opens when the pedal is pushed. I have figured out that there was a ground clip that came loose but I'm still searching for a short because the brake lights only work 10% of the time.
Once you verify that you have a 100% reliable brake switch in place, let's figure out the path that the
power intended for the brake lights out back has to travel. Here's the destination for the output
side of the (Stoplamp) brake switch. (White wire, circuit #17)
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(Section of wiring diagram showing Turn Signal Switch detail. Brake circuit big picture to follow.)
So first locate Circuit #
17 coming into the Turn Signal Switch on pin
P. For now, let's not modulate
the brake lights with either Left or Right turn signalling and that the Hazard Flashers are also off.
So with power on Pin #
17 in, we will have power out on Pin M (circuit #
18, Yellow wire to LH stop lamp)
and also Pin N. (circuit #
19, Dark Green wire to RH stop lamp.)
Pulling it all together, here's the Big Picture of the "Stoplamps" circuit, from brake pedal to brake lights out back, all on 1 sheet:
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Now let's take the wiring diagram functional perspective and try to turn it into a physical layout we can follow
in the real world:
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I'd like to stop here for a moment and recap. Essentially in the previous reply I've dragged us
all through the implementation specifics of the brake switch, followed by zooming in on the
Turn Signal Switch and discussing how the 'stoplamp' signal navigates through that.
But putting on my troubleshooter hat, I want to figure out if the brake lights are only working
10% of the time is because of a flaky switch up front, loose ground out back, or something inbetween?
Common sense me thinks that any part of the circuit that is forced to work outside gets checked over first.
If that all checks out, then it's time to figure out if it's a flaky brake switch, tired connections
inside the Turn Signal Switch, or something loose in the C100 > C101 > C400 path. And of course
the cleanliness of ground G410.
And just to give you an idea of what the factory troubleshooting flow look like for the
'Stoplamps Do Not Operate':
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I did the above mostly to introduce myself to the intricacies that the power from the brake pedal switch
(courtesy of the Stop/Haz fuse) must navigate in order to get those stop lamps out back to illuminate.
I hope that helps you with figuring out a fix. And if you don't already have access to a set of factory service
manuals for your machine, then don't hesitate to give yourself the good stuff. (
'88+ Service Manuals) Best of
all, the price is right.
Best of luck getting those stop lights back to 100% reliability. And let us know what the fix turns out to be.
Cheers --