Been going crazy trying to figure out why the brake lights don't work & gauge lights don't work. Blinkers work, but when I step on the brakes or turn on the headlights nothing lights up. I checked the headlight switch & no power on the black wire for the tail lamps or the Green/red wire for the Brake switch feed. Not sure if they are related but I was wiring up a new gauge panel & noticed the gauge lights don't light up. No power to the Blue/red wire. I did have 2 blown fuses. replaced one & the lights under the dash came on. The others were 14amp fuses & I didn't have any so just as a temporary fix I tried a 9amp, but no power on either side of the fuse. Not sure what to look at next. I tried to find a fuse block diagram to see which fuses power which parts but couldn't find one.
Tail/Brake Lights Don't Work
- Thread starter norcalsvt
- Start date
JDS68Stang
New Member
If worse does comes to worse and you can't solve the problems you can run a hot wire to your brake light switch and at least have them working (buy a fused line). Run a hot wire into the cab, hook on a tester to it and then touch to the brake light switch connectors, the one that DOESN'T light up your back brake lights is the one you want to splice and wire the hot wire to.
As for the headlights, did you say the switch is good? If so again you can run a fused hot wire to it also, sounds like you have a broken connection somewhere.
I don't have to tell you electrical problems can test your patience real quick.
As for the headlights, did you say the switch is good? If so again you can run a fused hot wire to it also, sounds like you have a broken connection somewhere.
I don't have to tell you electrical problems can test your patience real quick.
I will probably have to try this so I can drive the FB while the weather is still decent. So the brake s don't go through the fuse box?
Also, the light switch works for the front headlights. I thought it was strange that the blinkers work, but I guess the blinkers run on a different wire than the brake lights?
BarnStang
Founding Member
If you don't have a 12v test probe, go buy a cheap $5 one. Can't survive electrical problems without it. At least not very easily...
Power for the brake lights comes from the headlight switch, to the brake switch (on the pedal) then to the turn signal switch, and then to the brake lights. If you have turn signals, then the problem has to be the brake light switch or the wire coming from the head light switch. Sometimes the wires in the headlight switch can come loose and work their way out. Make sure all the connections in the plug are pushed in at the head light switch.
Dash lights can be a pain. The small fuse in the center sends power to the head light switch where it runs through the rheostat (dimmer). If the coil gets corroded, you will lose the dash lights. You can try to clean the wiper, but be careful you don't knock the carbon brush off the copper wiper. I have also seen (read ran around in circles for hours) where the wiper corroded between the wiper and the carbon. Dang! I had 12v at the wiper, but nothing on the coil. It finally broke off. New switch fixed that. You can take the headlight switch apart to clean the coil, wiper and glue the coil back into the ceramic if it's loose. Just remember how it came apart...I'll try yo attach an image of the wiring. ALso, the fuses and holders can be rusty. Make sure thats. not a problem. And lastly, I have run this problem into the ground at least three times. The wire, where it's crimped to the fuse holder clip on the backside of the fuse box, can become corroded and intermittantly make contact, or not at all. Take the 12v probe and press the point into the crimp to see if THAT'S the problem. Wiggle it around to get the wire to make contact with the fuse clip. THis is if you don't have power to one side of the fuse and you know you should. Meaning there is 12v on the wire but not the fuse clip...
Power for the brake lights comes from the headlight switch, to the brake switch (on the pedal) then to the turn signal switch, and then to the brake lights. If you have turn signals, then the problem has to be the brake light switch or the wire coming from the head light switch. Sometimes the wires in the headlight switch can come loose and work their way out. Make sure all the connections in the plug are pushed in at the head light switch.
Dash lights can be a pain. The small fuse in the center sends power to the head light switch where it runs through the rheostat (dimmer). If the coil gets corroded, you will lose the dash lights. You can try to clean the wiper, but be careful you don't knock the carbon brush off the copper wiper. I have also seen (read ran around in circles for hours) where the wiper corroded between the wiper and the carbon. Dang! I had 12v at the wiper, but nothing on the coil. It finally broke off. New switch fixed that. You can take the headlight switch apart to clean the coil, wiper and glue the coil back into the ceramic if it's loose. Just remember how it came apart...I'll try yo attach an image of the wiring. ALso, the fuses and holders can be rusty. Make sure thats. not a problem. And lastly, I have run this problem into the ground at least three times. The wire, where it's crimped to the fuse holder clip on the backside of the fuse box, can become corroded and intermittantly make contact, or not at all. Take the 12v probe and press the point into the crimp to see if THAT'S the problem. Wiggle it around to get the wire to make contact with the fuse clip. THis is if you don't have power to one side of the fuse and you know you should. Meaning there is 12v on the wire but not the fuse clip...
BarnStang
Founding Member
thanks for the wiring. I took the connector apart from the light switch & I have power coming in on the Blk/Orange but no power to the brake wire or the taillight wire. I did wire power to the brake switch on the green wire & the brake lights came on. Somehow power is not getting to the brake light wire on the light switch module. I pushed the pins in & no difference.
Not sure if this means the light switch is bad or the plug in module is bad
Not sure if this means the light switch is bad or the plug in module is bad
BarnStang
Founding Member
Hmmm, it would seem the switch is not working, but what do you mean by the plug in module? The part that plugs into the headlight switch is just the end of the wiring harness. It's only function is to hold the wires. Sorry, just wanted to make sure we are talking about the same thing. With the wiring harness plug disconnected from the headlight switch, there is no way for power to get out onto the other wires. Need to check that with the headlight switch connected to the harness.
Or, you can check the switch out with it on the work bench. Only problem is that I thought I had this really great graphic of the headlight switch but can't find it. I would REALLY like to have that one again. Does anyone have that graphic? The one the shows how the headlight switch is wired inside?
Check the green w/red wire (#10) again with the switch conneced. This is where you make sure none of the wires are pushing back out of the plug. You will know if one is sticking out. You should not see any metal part of the crimp sticking up and, unless it's really bent or sitting crooked, should slide into the connector when you push on it.
Or, you can check the switch out with it on the work bench. Only problem is that I thought I had this really great graphic of the headlight switch but can't find it. I would REALLY like to have that one again. Does anyone have that graphic? The one the shows how the headlight switch is wired inside?
Check the green w/red wire (#10) again with the switch conneced. This is where you make sure none of the wires are pushing back out of the plug. You will know if one is sticking out. You should not see any metal part of the crimp sticking up and, unless it's really bent or sitting crooked, should slide into the connector when you push on it.
I thought that when I pulled the wiring harness from the headlight switch it would have power on the green/red wire. It makes sense now that the knob would need to be pulled out to have power on that wire. I will try again tomorrow with the harness plugged back in.
Tested for 12v when the headlight switch is out & wheel turned. No power on the brake switch feed or tail lamp feed. I found a head light switch diagram so I was able to figure out the R is Tali Lamps when the switch is pulled out & A is for the brake switch feed that I assume should always have 12v since this is wired to the brake switch. Also, the I which is for the dash lights has no power either. What I'm not sure is for the 3 that need power does it come from the B terminal or from the fuse box? I believe the dash lights(blue/red) come from the fuse panel & that has power on the back side but nothing on the fuse side. I believe the contacts may be bad. I can't figure out where the power comes from for the brake & tail lights. If it's from the switch itself then I guess it's bad?
BarnStang
Founding Member
Power for the dash lights comes from the small fuse in the center of the fuse panel. from the fuse, it goes to the headlight switch where it goes through the wiper onto the coil then to the dash lights terminal leaving the headlight switch. or into the coil and out the wiper-whichever way it actually goes i'm not sure.
If you have power going into the switch with the plug connected, and the switch on (out) and no power on the brake light line then the switch must be faulty. actually, for the brake line, the switch does not have to be on (out).
One last test to make sure. Can you jumper 12v to the headlight switch plug on the wire that goes to the brake light switch? Make sure its not the wire. I doubt it is the wire, but make sure at least for that circuit. I think it's time to try a new switch.
If you have power going into the switch with the plug connected, and the switch on (out) and no power on the brake light line then the switch must be faulty. actually, for the brake line, the switch does not have to be on (out).
One last test to make sure. Can you jumper 12v to the headlight switch plug on the wire that goes to the brake light switch? Make sure its not the wire. I doubt it is the wire, but make sure at least for that circuit. I think it's time to try a new switch.
Thanks for all your help. I jumpered 12v to the brake light wire & the tail lights came on when I stepped on the brake pedal. I also jumpered the black wire which I think simulated the switched pulled out & the brake lights were lit. I am going to order a new switch.
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