Brake light issue (Page 4/5)
stevep914 MAR 18, 12:17 PM
And as an afterthought, the connector for the rear of the brake switch seems to be able to plug in either frontwards or backwards. Would switching this around give me a different result? I notice that this connector looks like it could be reconnected going either way.
stevep914 MAR 18, 02:19 PM
More confusion: the brake light switch has two connectors- one closest to the plunger has a white wire and an orange one. The rear connector has two wires; one purple, and one pink. With BOTH connectors dismantled from the brake light switch, my brake lights are still on. I have not meddled with this switch ever, and it did work properly until I had the big ground failure ( and that darn cooling fan relay connection fried) .
stevep914 MAR 18, 03:54 PM
Sorry if I am rambling, but I am doing this a step at a time. I found out which power wire in my harness runs the brake lights. It goes to the C500 into the module at the top closest to the firewall. I pulled the C500 apart, and my brake lights went off. I then reconnected both brake switch connectors at the pedal, reconnected the C500 halves, and now I have no brake light function at all. Fuse is ok.All other lights , tail, and signal, and hazards work. To clarify something: this car has 4 Carillo Ferrari F40 OEM tail lights. The brake and tail lights are red, with 2 separate bulbs in each light. The turn signal and hazard flashers are in the yellow lights with 2 bulbs in each. At least the brake lights are not on all the time now, but where do I start now to get brake light function back?
olejoedad MAR 19, 07:11 AM
The brake switch can be removed and disassembled.

One terminal should be Normally Closed, the other should be Normally Open.

The brake lights are wired to the Normally Closed terminal.
stevep914 MAR 19, 09:30 AM
Thankyou! There are four terminals on my brake switch; two on top near the plunger, and two on top near the rear of the unit. Do I test both sets?
theogre MAR 19, 10:34 AM
1. You pull the plug on the switch and brake lights stayed On... Is not a switch problem that cause On and likely now that is going to happen again.

2. PULLED C500 and light won't work Is Very likely now Not a pedal switch problem. Just Jumper the org & white wires on the pedal switch tells you instantly when light go on.

If light On while jump white wire...
can be the switch itself or plug w/ loose terminal(s). If the car Is Not a GT...

Switch w/ white wire should be open when the pedal or you is "pressing" the tip in. Closed otherwise. Tech terms is "Normal Close" but many get confuse because how is used in the car.

Other section(s) of pedal switches can be NO or NC depending on other options.
Examples:
All 86 should have lt Blue wire. Jump that to Orn then High Brake turns on. IF is a GT then the Blue Wire turns makes Brake Light turn On too.
If car had Auto Trans from factory, 1 sections has pnk/blk and purple wires to run TCC locking.

Go back to C500. Look for 1 white wire what go nowhere with both ends in the C500. If there, It just jumpers C500 C7 and H8. If there even if cut tells fast if was any notchy or GT.

Note that Should have Taillight Wiring "Thinks" is a GT because of...

quote
Originally posted by stevep914:
To clarify something: this car has 4 Carillo Ferrari F40 OEM tail lights. The brake and tail lights are red, with 2 separate bulbs in each light. The turn signal and hazard flashers are in the yellow lights with 2 bulbs in each.


But how done by builder is anyone's guess.
sanderson231 MAR 19, 01:05 PM

quote
Originally posted by stevep914:

More confusion: the brake light switch has two connectors- one closest to the plunger has a white wire and an orange one. The rear connector has two wires; one purple, and one pink. With BOTH connectors dismantled from the brake light switch, my brake lights are still on. I have not meddled with this switch ever, and it did work properly until I had the big ground failure ( and that darn cooling fan relay connection fried) .



The white and orange wire are for the brake lights. This switch closes when the pedal is depressed.

A pink wire w/ black trace and a purple wire are for a switch associated with torque converter lock-up. This switch is normally closed and is a permissive for torque converted lock-up.

There could be a third brake switch for cruise control. This would have a gray wire and a brown w/ white trace wire. This switch would be normally closed and is a permissive for cruise control
stevep914 MAR 19, 07:44 PM
Well, after fiddling around some more this afternoon, I am ready to just run a complete new set of wires from the brake switch to the brake lights. The damn lights are back on again all the time , the second the power is turned on . I disconnected the harness to the lights, put direct battery power to the brake light wires at the bulb bracket, and they come on; but so do my cooling fans! There must be so much stupid customized wiring in this car, nobody could get it all sorted out. I really appreciate all the suggestions and advice, but it would appear this car is a one off, with no stock guidelines. As a last request, I am assuming the brake light circuit is basically a big loop with the switch as an interrupter, and that the wiring for this loop would be hot, assuming the grounds on the bulb brackets work? And that I would disconnect any existing power source, whether it currently works or not, at the brake bulbs? Thanks again to all of you! Steve
theogre MAR 19, 08:45 PM
If you put 12v anywhere...
You can have weird things happen or even start a Fire in a short circuit.

Even a 100% Fiero blowing fuse(s) or have bad bulbs or grounds can do weird things covered in https://web.archive.org/web...rocave/sneakpath.htm

[This message has been edited by theogre (edited 03-19-2023).]

sanderson231 MAR 22, 03:05 PM

quote
Originally posted by stevep914:

Well, after fiddling around some more this afternoon, I am ready to just run a complete new set of wires from the brake switch to the brake lights. The damn lights are back on again all the time , the second the power is turned on . I disconnected the harness to the lights, put direct battery power to the brake light wires at the bulb bracket, and they come on; but so do my cooling fans! There must be so much stupid customized wiring in this car, nobody could get it all sorted out. I really appreciate all the suggestions and advice, but it would appear this car is a one off, with no stock guidelines. As a last request, I am assuming the brake light circuit is basically a big loop with the switch as an interrupter, and that the wiring for this loop would be hot, assuming the grounds on the bulb brackets work? And that I would disconnect any existing power source, whether it currently works or not, at the brake bulbs? Thanks again to all of you! Steve



An 86 had an "engine blower assembly" from the factory. The blower and the associated relay were located under the carpet on the right side of the trunk. The blower discharged into a manifold on the trunk wall which cooled the alternator and coil/distributor via some ~1" tubes connected to the manifold. This blower was fed by the Fan "E" fuse which is a "hot in run" circuit. This same fuse fed the "Pontiac Emblem" lights on the GT models. According to the FSM these light would be on whenever the key was in "run".

Perhaps the OEM engine blower was removed and replaced by new fans. It would make sense to re-purpose the OEM relay ( it might have been relocated to the firewall). Whoever did the conversion may have connected lights to the "Pontiac Emblem" wires. If so, these light would be on all the time. The hot wire is a brown/white wire from G9 on the C500 connector. If 12V is applied to this wire at the lights and the fans are wired as GM did it, then the relay will energize and the fans will run.

I suggest pulling the Fan "E" and seeing if that prevents the lights from coming on.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged