Going coast to coast without a clue

[SanderGA]

So, I bought a 93 HPC on Bring a Trailer back in June. The car was in Salt Lake and I live in Atlanta so I visited it for a few days in August. Great car. Picked it up from Salt Lake yesterday with plans to tour the southwest and drive it home.

Yesterday I made it from Salt Lake to Moab. Got caught in traffic and had to pull over as the water temp reached 110 Celsius.

I woke up and confirmed the radiator fan does not work. Also went to change a faulty turn signal bulb but the bulb is not the problem.

Then I discovered there are no brake lights.

Brake lights are the top priority. Tried changing the builds to no avail.

Opened the pedal box and tested the connections on the switch shown in the photo. There is not a positive current on either side of that switch. I assume that means I’m one step closer to a solution. Can someone confirm it is that switch that activates the brake lights? I assume so but I’m concerned I’m addressing the problem there when there is another switch in the hydraulic system that’s activating the brake light.

Thanks in advance for any assistance.

[yellowss7]

99% sure that switch is the only one to operate the brake lights. On mine it was just a matter of tightening the locknut up to make sure it made contact with the plunger when the brakes were depressed. Good luck ��

althought that switch does look pretty groaty. May be worth cleaning up a bit. Just be careful if you try to open it up. That spring will try to escape. And it’s really good at getting lost. 😂

[SanderGA]

So. Traced the wires. There’s a blue wire on one side of that switch and a green on the other side. They are bundled together and leave the pedal box. The bundle is then split open. In the open section, the blue wire is soldered to a blue wire. The green wire is soldered to two green wires. They are then bundled back up and are bundled with many other wires in what I assume is the main wiring harness. At the back of the car, each brake light is powered by a green wire.

The problem seems to be that the blue wire is supposed to carry power to the switch. When the brake light switch detects the pedal is pressed it’s supposed to release power to the green wire(s) and the brake lights work.

It seems I need to run 12v of power to the blue wire which is pretty simple unless there’s a relay in the circuit.

Any thoughts?

[SanderGA]

99% sure that switch is the only one to operate the brake lights. On mine it was just a matter of tightening the locknut up to make sure it made contact with the plunger when the brakes were depressed. Good luck ��

althought that switch does look pretty groaty. May be worth cleaning up a bit. Just be careful if you try to open it up. That spring will try to escape. And it’s really good at getting lost. 

Thank you for the reply. The switch does look bad but the plunger does move and fully release when the brake pedal is pressed. If there was positive current on either side I’d be cleaning it like crazy. But with no current on either side I’m not sure what good it will do.

[JohnCh]

You mention a faulty turn signal as well. Do any of the other lights (running, F/R signals, side lights) have issues? Have you checked the fuse box for a faulty connection? Curious if the fan issue is also lack of 12v+ reaching the switch or motor?

-John

[SanderGA]

Earlier, neither side of the brake light switch had power. Pulled the switch so the guys at NAPA could marvel at it and tell me it was unique and there wasn’t another on the planet. Tried a test lead from the positive terminal on the battery to the green wire and got a spark to the frame and no brake lights. Pulled all the fuses for the second time today. First time I visually inspected them. Second time I tested them. One was bad. Not sure if it was bad before or if it went bad when the test lead sparked. Replaced it and put the switch back in. Tested the input and output and the green side had a current. One brake light started working. Put the original bulb in the other socket and now it’s working. So I have brake lights.

Still no right rear turn signal no matter which bulb I use. Radiator fan is next.

[ahavams]

Congrats on picking up the car! I’m not much help on the electrical issues, but wanted to wish you a fun and safe trip! Not sure how far West you plan to travel but would love to meet up if you make it out to Los Angeles.

[SanderGA]

So the brake light problem could have been a stick switch that came unstuck or a bad fuse. I think it was a bad fuse.

No power is going down the lead to the radiator fan at 95 Celsius. I‘ve unplugged it and I’m wiring in a manual switch in the cockpit. With dedicated auxiliary wiring the fan runs great. I’ll just have to act as a human thermostat.

Turn signal remains a mystery but we all need a little mystery in our lives.

Tomorrow I’m heading to Bryce Canyon.

[pksurveyor]

https://www.summitracing.com/parts/a...MobileSwitchNo

The brake switch is available at Advance Auto.

[pksurveyor]

https://shop.advanceautoparts.com/p/...archTerm=brake light switch