Ever since my recent electrical engine stop failure ( which with a lot of help here we solved, being a ground strap problem): my rear brake lights are on whenever the power is turned on. I have a racing style cutoff switch at the battery which renders the battery disconnected from the car when it is turned off. Turning this on makes the whole car function, but has my brake lights on all the time. I went at the brake light switch at the pedal, and disconnected it, and the brake lights are still on. Wiring on this car is a nightmare, where it being a kit car, a lot of the stock wiring was played with by the previous builder, although most of the wiring harnesses appear to be stock. Looking at the Haynes manual for the brake light wiring, it shows a relay in the brake light circuit for each rear stop light; I am presuming somewhere before the stock harness goes from the connector from the firewall, to the harness to the rear stop lights. I can’t find one on my car. I DO remember, when the other problem occurred, my two rear cooling fans quit working, and were powered through a relay that sat next to the fuel pump relay on the firewall. The connector to this relay was partially burnt. Testing the wires into this relay showed none of them functioning whether the power was on or not. Currently, those wires, being non functioning, are taped off, with no relay where it used to be. Are there stop light relays anywhere in the stock system? As this seems to be the only noticeable variant from when everything worked before the problem, should I be concentrating my search for a solution there? Thanks in advance! This forum and its members are a wealth of information! Steve
Ignore Haynes Rag of a book. Has so many problems and several versions too that changes whatever errors.
Year of car and model even has posted before. GT uses different taillight then others and can matter here.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
In 84 one of the three turn/stop bulbs in the back had a relay. No relay on the other two bulbs but power from the brake switch did go through the stalk.
In 88 no relay / no stalk - from the brake switch straight to the bulbs.
Don't know for sure about other years but suspect that 84 is a loner
If you have cruise there are two brake switches; one for the stop lights and one to disable cruise when brake pedal is pushed.
------------------ formerly known as sanderson 1984 Quad 4 1886 SE 2.8L 1988 4.9L Cadillac 1988 3800 Supercharged
Mine is an 86 chassis, 2.8 v6. The relay that used to power the engine compartment cooling fans had a connector that appeared ( by the number and color of the wires) to be for an air compressor. But my car has no A/C. It was still providing power, although not after the electrical fail issue. If there were stop light relays, where would they be located? I really don’t see any.
Originally posted by stevep914: If there were stop light relays, where would they be located? I really don’t see any.
I found a digital copy of an 86 factory service manual, I had buried on my desk top. In 86 there were no relays. The SE models had the power from the brake switch through the stalk to the bulbs. The GT model had power from the brake switch straight to the bulbs.
------------------ formerly known as sanderson 1984 Quad 4 1886 SE 2.8L 1988 4.9L Cadillac 1988 3800 Supercharged
Thanks for the suggestions! I guess I am going to have to stumble my way step by step ; I hate electrical issues! I doubt it is the switch at the brake pedal; with the connector disconnected there, the brake lights are still on all the time when the battery interrupter switch is turned on.
Originally posted by stevep914: Mine is an 86 chassis, 2.8 v6. The relay that used to power the engine compartment cooling fans had a connector that appeared ( by the number and color of the wires) to be for an air compressor. But my car has no A/C. It was still providing power, although not after the electrical fail issue. If there were stop light relays, where would they be located? I really don’t see any.
Again.... Model. GT? Or Other?
No Fiero have Relays for Taillights except 84 that "Played Tricks" w/ Taillights to have 3 bulbs per side Active as stop/turn. All others only 2 bulbs per side for stop/turn. GT has Amber Rear Turn and Turn Signal is wired for 2 more bulbs.
Brake Pedal have often have 2 Switches w/ or w/o cruise. If have unplug all plugs there then Is Not a pedal or switch problem keeping taillights on.
If taillight stop/turn or GT turn is "On" check front turn bulbs too. If all are On... Likely the Hazard switch is On but has problems and no Flashing. No flashing could be bad grounds or Flasher is bad.
Ogre, thanks, I am digesting this…. Today, I unplugged what looks like a stock 10 pin connector on a harness that comes from the firewall, and when connected, feeds a harness that goes to all the rear lights on the rear clamshell. The colors of the wires on each side of the connector are identical. Again , this looks stock. I am trying to determine which wire feeds the current to the stop lights, and which is the ground. I should be able to get the stop lights to turn on by completing a direct -from- battery circuit applied to these two wires off the pos and neg post of the battery- correct? So far I am not having any luck, as there are many pos and neg combinations depending on which wire does what. The connector has pins labeled ABCDEFGHJK. Pins BHJK are plugged with no wires. A is orange, C is light blue, D is dark blue, E is dark brown or black, F is white, and G is light green. Of course none of these make any sense on the Haynes wiring diagram. ( I know, ignore Haynes, but it is all I have got to work with. ) it would be a great start to know which color wire is the feed from the brake pedal switch, and which is the ground. I am assuming all the remaining wires operate the turn signal lights and rear night driving lights. All that stuff works normally, when the connector is connected, except the brake lights are on all the time. I have tried many combinations of positive and negative to all the wires, and so far cannot get the brake lights to come on. And when I plug the connector together and turn the power on, the brake lights come on all the time, whether the engine is running or not. #*€§!
Steve, I don't know if this could be of any significance... but there have been reports over the years of funky taillight behavior when the rear taillight harness ground becomes corroded and/or detached from the frame.
[This message has been edited by Patrick (edited 03-13-2023).]
Patrick, I will have a look tomorrow. The whole rear end of my frame has been modified for the Ferrari body. I am not sure I even have that there. My harness is on the driver’s side of the car, and I do not see any ground wires coming out of it anywhere, but will check. It was grounding problems that started this whole electrical mess.
Originally posted by stevep914: The connector has pins labeled ABCDEFGHJK. Pins BHJK are plugged with no wires. A is orange, C is light blue, D is dark blue, E is dark brown or black, F is white, and G is light green.
These wires and plug are for something else.
For Non GT models: White wire from pedal switch goes to turn switch Thru Pin P @ C210 a big flat connector on steering column. Often hidden by column trim. GT model uses Blue wire from pedal switch direct to C500 for Brake lights.
Wires for Taillights: Yellow, L turn and brake Dk Grn, R turn and brake Brn, park lights Blk, ground
Most of Those wires also go thru C210 then C500 in the engine bay next to the OE battery or location if moved the battery.
Unfortunately that is the harness I have, whether it was designed for something else or not. I guess I am just going to have to trial and error it to find what wires do what. I am still going on the assumption that one of those wires is a ground, and one is the trip wire to turn the brake lights on. The harness after the connector s imbedded in the fiebreglass of the clamshell, so it is not possible to trace each one back from the lights to the connector. The harness from the connector to the firewall appears to go through where it is supposed to. The joys of owning a car that was customized by someone else!
Thankyou much for the wiring diagrams! I hope they will help me. Because this is a replica Ferrari that has been extensively modified, I only know it is an 86 chassis with a 2.8 engine and Isuzu 5 speed. I do not know if the car was an SE or GT, which appear to have different tail light wiring. As Ogre had suggested, the wiring harness that was used, is not the stock Fiero setup, and the wire colors are all different. In theory, I should be able to trace the wiring from the stop lights back through the harness, but whoever built the car fiberglassed in the harness, all along the side of the rear clamshell, so the wire colors at the light are different than what shows up at the connector that hooks up with the wire loom that goes through the firewall. Lesson learned if I were ever to build one of these from scratch! I am hoping to start by determining a ground wire in the loom, and then direct testing off the battery to determine which other wire activates the stop lights. Should be just a direct circuit through the bulb, right? Assuming so, then I have to find the corresponding wire on the connector for the firewall loom, that is triggered from the brake pedal switch to tell the lights to turn on.
I'd hate to think that this was a GT and someone half-assed the "Pontiac" logo wiring into the tail light circuit. Then when the key is on, the "Pontiac" illuminates but in reality your taillights illuminate.
Had not thought to do that with a voltmeter, I have been trying to use a test light going direct from positive terminal on the battery ( with the harness disconnected) to try to find my ground wire. There are many possible connections on the pins for positive and negative, so this isn’t easy. Sounds like I would have to strip back coverings on the wires at the lights and then try the continuity thing. I will try to do that. At that point I know what wires do what on the lights end of the harness, before it is connected to the other wire loom coming through the firewall.THEN. I have to figure out why the corresponding signal wire from the switch is keeping the lights on all the time. Funny, but with the connector at the pedal switch disconnected, my lights are still on when the power from the battery is turned on.
Originally posted by olejoedad: No need to strip wires, you can remove the bulbs. The barrel of the socket is the ground and the tabs on the bottom are the positive.
Yes, don't strip wires just to check... Do remove bulbs.
If can't remove bulbs for other wires, Careful use of strong sowing needles to pierce the insulation or back probe plugs is much easier. If pierce a wire, coat the hole w/ silicon or brake grease to keep out water.
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
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
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.
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!
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.
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.
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
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?
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.
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) .
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?
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.
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
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
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.
------------------ formerly known as sanderson 1984 Quad 4 1886 SE 2.8L 1988 4.9L Cadillac 1988 3800 Supercharged
