Brake light issue (Page 3/5)
sanderson231 MAR 15, 11:34 AM
The stop lights are grounded all the time. There is no switch in the ground circuit. So it makes no sense to trace out ground circuit.

Here is what I would do:

1) Pull the 20A stop-hazard fuse. This should kill the lights. If it doesn't then there is a non-OEM circuit that is powering the lights. Assuming that pulling the fuse kills the lights, put the fuse back in

2) Pull the hazard flasher from the convenience center (chime box located under dash on the passenger side. The flasher is an aluminum cylinder. The flasher may be fused in on position causing lights to stay on.

3) If 2) doesn't work then disconnect the C210 connector. It is a flat connector located under the middle of the steering column with six wires:

white
purple
brown
dark blue
yellow
dark green

This will eliminate a problem in side the turn signal stalk

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

olejoedad MAR 15, 11:48 AM

quote
Originally posted by sanderson231:

The stop lights are grounded all the time. There is no switch in the ground circuit. So it makes no sense to trace out ground circuit.

Here is what I would do:

1) Pull the 20A stop-hazard fuse. This should kill the lights. If it doesn't then there is a non-OEM circuit that is powering the lights. Assuming that pulling the fuse kills the lights, put the fuse back in

2) Pull the hazard flasher from the convenience center (chime box located under dash on the passenger side. The flasher is an aluminum cylinder. The flasher may be fused in on position causing lights to stay on.

3) If 2) doesn't work then disconnect the C210 connector. It is a flat connector located under the middle of the steering column with six wires:

white
purple
brown
dark blue
yellow
dark green

This will eliminate a problem in side the turn signal stalk




Good advice.
stevep914 MAR 15, 07:55 PM
Wow! Some great advice! I will try all this in the next day or so.I Did manage to find out which wire in my harness will turn the brake lights on, with the connector disconnected ( whole light assembly not connected to anything) just as an aside: when my original electrical failure problem surfaced, I mentioned that my rear cooling fans were powered through a relay beside the fuel pump relay. ( obviously not a stock setup) The connector for that relay was cooked, and the cooling fans powered by it did not turn on anymore. I traced the wire harness for the three wires out of the relay, and it goes to the C500 box into a plug in at the top firewall side of the C500 box. The relay has been removed, and the wires taped off. Just coincidental that the stop light problem kicked in with the failure of that relay connection? Mucking around today, I also discovered one of the two power wires going into the passenger side stop light socket was broken, and only one of the two bulb filaments would light up. That wire appeared to be possibly grounding against the metal light socket bracket, which has a ground connection on it. After repairing that, I still have the problem.
sanderson231 MAR 15, 10:37 PM

quote
Originally posted by stevep914:

I mentioned that my rear cooling fans were powered through a relay beside the fuel pump relay. ( obviously not a stock setup) T



The A/C relay is in that location on a stock Fiero. If there is no A/C maybe the A/C relay was repurposed for the fans.
stevep914 MAR 16, 09:53 AM
That is my belief. And when the problem occurred with total electrical failure, the fans stopped working, and I found the fried connection at the relay. . Also someone mentioned the lights are permanently grounded ( to the frame, I presume ) on a stock car. My clamshell the lights are mounted to, is all fiberglass, so there has to be a ground wire in the wiring harness to the lights. I will try these other tests today, hopefully Thanks all!
sanderson231 MAR 16, 11:41 AM
What I was trying to convey is that there are no switches on the ground side of the lights. The grounding is via wires from the light sockets. There are three paths to ground:

G504 which is a stud below the throttle body on the engine
G201 which is behind the instrument cluster
G202 which is underneath the console below the ECM

A ground wire goes through C500-F10 and then back through the passenger side firewall grommet to get to G201 and G202.

Since your lights are on all the time, there is a path to ground. The problem is on the hot side - how come there is always 12V going to the lights

On SE models the hot wire path is:
-from the stop/hazard fuse
-to the brake switch
-through the passenger side firewall grommet
-to C500 G7
-to C500 H8 (just loops around)
-back through the passenger side firewall grommet
-to C210-P (connector for turn signal stalk)
from C210-M and C210-N (2 wires)
through the passenger side firewall grommet (2 wires)
-to C500-H7 for the left lights and to C500-J8 for the right lights

On GT models the hot side path is:
-from the stop hazard fuse
-to the brake switch
-through the passenger side firewall grommet
-to C500 G7 and then to the left and right lights

For SE models the hazard light circuit provide a parallel path around the brake switch
-from the stop/hazard fuse
-to the hazard flasher
-to C210-K
from C210-M and C210-N (2 wires)
through the passenger side firewall grommet (2 wires)
-to C500-H7 for the left lights and to C500-J8 for the right lights (two element tail-stop-turn)

For GT models the hazard light circuit provide a parallel path around the brake switch
-from the stop/hazard fuse
-to the hazard flasher
-to C210-K
from C210-M and C210-N (2 wires)
through the passenger side firewall grommet (2 wires)
-to C500-H7 for the left lights and to C500-J8 for the right lights (one element turn light)

Are you sure it is the brake lights that are on all the time and not the tail lights. If pulling the stop/hazard fuse does not kill the lights, try pulling the taillight fuse.
stevep914 MAR 18, 10:09 AM
Finally got time to check this out. I pulled the 20 amp hazard fuse, and the lights still come on. It Is the brake light circuit that is on all the time. So it would appear I have a non OEM hot circuit for powering the brake lights. All other tail light / signal light functions are normal. Even though the brake lights are always on, the hazard flashers, when engaged, show a pulsing of the brake lights. The only real variable since this whole mess started is the failed function of that relay that was powering the cooling fans. That relay has been removed, and the three wires from it are taped off. As these wires are also non OEM, so God knows how to determine how to reinstall a replacement relay, and what it will do? Other than running totally new wires from the brake pedal switch to the brake lights, I am still stumbling around here.
sanderson231 MAR 18, 11:06 AM
Next step

1) disconnect negative terminal on battery
2) separate the C500 connector. Unscrew small bolt with 1/4" head in the middle. Then pull the connector apart
3) reconnect battery
4) are the brake lights still on?

This will help isolate where the mystery source of power is

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

stevep914 MAR 18, 12:10 PM
Ok, digging around from the start of the brake light circuit. I disconnected the two prong plug at the rear of the brake switch. I ran a direct negative wire from the battery to one pin on the switch and a positive wire from the battery to the other pin on the switch, and my test light comes on showing a completed circuit— WHILE THE BRAKE PEDAL IS NOT DEPRESSED. My test light goes out when the brake pedal is depressed, disrupting the circuit. Is this not backwards?? Should not I have an active circuit when the brake pedal is depressed, sending a signal to turn on the brake lights? As a side note, there are two wires that connect to the front of the brake pedal switch. They were still connected when I did this test. Would they affect my test results?
stevep914 MAR 18, 12:14 PM
Sanderson, I had not seen your post before I sent my last one. Before I do as you suggest, am I off base on my brake pedal switch test?