Brake, tail, turn signal, back up lamps?

[ChaseDale3and8]

Okay guys, got another problem that has come up on my 86 K10 since I got it back up and running again. The right side brake light doesn't work, neither back up lights, and neither turn signal on either side. When I put the hazards on, only the left side works at the rear, and both fronts work. I replaced the flasher, found the tail light ground was bad on the left side (couldn't find one on right side) checked the grounds at the front, and still can't figure out what the problem is. It was once wired for a trailer hook up by a PO and I'm beginning to think this may be where the problem is. All of it was working fine until recently. I changed the bulb on the right side as well. It looked like it got hot right before it burned out as it was disclolored. Anybody know what might be causing the trouble? Also forgot to mention that both tail lights DO work. Thanks in advance! ....Joe

[Irish_Alley]

make sure you have good contact in the socket, you also have a ground on the frame from the wire loom. make sure the trailer harness isnt the problem. and make sure you have the right bulbs in the sockets. the back up lights could be another problem (Back-Up Light Switch) so just worry about your brake lights for now.

[ChaseDale3and8]

Thanks for the reply. I checked the socket. It looks good and the bulb has good contact with it. Which color wire goes to what on these trucks? I'm thinking I might just try and cut that trailer plug out altogether and see if I can get power to the right brake light. Does the back up light switch have something to do with it too? All of the lights have always worked until recently, then they quit to where all I have is left rear brake light and tail lights on both sides.

[Irish_Alley]

i would check to see if your getting power to the respective wire for brakes and turn. check at your trailer wire harness also. i think from factory there should be a 4-flat connection behind the bumper check there also. idk if the back up light switch is your problem with your lights but you might fix it by doing something else, the switch might be good. do you have any back feed in any other lights while your turn signals is on?

[Boone83K10]

Okay guys, got another problem that has come up on my 86 K10 since I got it back up and running again. The right side brake light doesn't work, neither back up lights, and neither turn signal on either side. When I put the hazards on, only the left side works at the rear, and both fronts work. I replaced the flasher, found the tail light ground was bad on the left side (couldn't find one on right side) checked the grounds at the front, and still can't figure out what the problem is. It was once wired for a trailer hook up by a PO and I'm beginning to think this may be where the problem is. All of it was working fine until recently. I changed the bulb on the right side as well. It looked like it got hot right before it burned out as it was disclolored. Anybody know what might be causing the trouble? Also forgot to mention that both tail lights DO work. Thanks in advance! ....Joe

if your truck is a fleetside, it only has one ground for the tail lights on the driver side.

[upload the image if it is yours, the source doesn't allow linking -admin]

I had this same problem, except my B/U flashed with the left turn signal and came on when I pressed the brake.

I would first test the trailer harness. If you don't need it then rip it out. There should be a rubber plug with 4 prongs near the middle of the truck behind the bumper. Unplug that and use a test light. Turn left signal on, right signal etc etc..testing all prongs each time. You should have only one prong lighting up except when you press the brake/hazards. If that turns out fine then it is in the trailer/rear harness. If not, then trace the wiring from the rear all the way to the firewall. My wiring had melted from being on the exhaust above the axle so make sure yours' is all good. You will lose track of the wire loom at the gas tank. It moves to the outside of the frame rail under the cab. It will run up all the way to the bulkhead connector.

You can take off the bulkhead connector and test it to see if everything coming from under the dash is ok. remove the neg battery connection at the battery. Use socket to take off bulkhead connector on firewall. The tail light section is on the right when looking at firewall from front of truck.

You can slide this out of the bulkhead harness. You must plug the rest back in to make the tests as it powers the inside of the cab. Connect the NEG back to the battery. Perform the same tests as you did on the rear plug to the bulkhead connector that is on the firewall. If all checks out then you know that everything under the dash is good. This tells you that something is wrong with the wiring from the firewall to the rear tail harness.

If not then you must continue searching under the dash. It could be at the neutral safety switch, wiring going into column, brake switch... who knows. Let's hope it isn't in the dash...