Front marker lights and turn signals illuminate when brakes are applied

[Jiblackledge]

Just completed a complete install of a Painless wireing harness on a 1979 C30 crewcab with all new led lights, the problem is the turn signals will not work and when the brakes are applied the front turn signals and front marker lights come on, the strange thing is this happened with the old orginal harness, and all the old lights, went to investigate and the wiring under the dash was a mess, so this was the reason for the new harness, I also changed the turn signal switch in the column, allgronds are installed properly, instructions were followed to the letter, there are multiple grounds from thr frame to the body and frame and the engine. Also did a 5.3 LS 4L60E swap with a PSI conversion harness. This is a father and son project we just finished and started to drive this past weekend, need ti get it figured out so we can keep driving and not get stopped, any suggestions on where to start would be greatly appreciated.

 

[Ricko1966]

Put incandescent bulbs back in it see if it works right then. Then we know if it's a wiring problem or incompatible lights,and yes that's a common problem with squares and leds.

 

[jcperformance]

Just completed a complete install of a Painless wireing harness on a 1979 C30 crewcab with all new led lights, the problem is the turn signals will not work and when the brakes are applied the front turn signals and front marker lights come on, the strange thing is this happened with the old orginal harness, and all the old lights, went to investigate and the wiring under the dash was a mess, so this was the reason for the new harness, I also changed the turn signal switch in the column, allgronds are installed properly, instructions were followed to the letter, there are multiple grounds from thr frame to the body and frame and the engine. Also did a 5.3 LS 4L60E swap with a PSI conversion harness. This is a father and son project we just finished and started to drive this past weekend, need ti get it figured out so we can keep driving and not get stopped, any suggestions on where to start would be greatly appreciated.

Since the problem persisted after a full harness swap, the issue is likely a bad ground at the rear light housings or a faulty bulb socket. Even if the frame is grounded, the light housings need a solid connection to the body or frame to prevent power from "backfeeding" through the front turn signal circuit when you hit the brakes.

 

[Jiblackledge]

Thanks for your replies, I will check the grounds on the rear again, we made sure they were connected to a fresh clean spot on the frame, I can also add it to the bed as well, and if that does not work I'll look into changeing back to the original style lights, again this was happening with orginal lights and harness.

 

[Jiblackledge]

Update for the light situation, the problem was that the hazard button was stuck in the on position once I fixed that to where it will work properly, now all the lights work as they should. No more front marker and turn signals coming on when the brake pedal is pushed and now the turn signals work. Thanks for the comments.