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Brake lights/hazard/turn signal problems

Hi there, having problems with my Brake lights/hazards/turn signals. If I turn the truck on (acc on, engine not on), my brake lights don’t work (sometimes the right one does, sometimes it does’t - seems to depend on how recently I touched turn signals/hazards 9last 10 min or so…). If I turn the hazards on, the passenger side light blinks, the drivers side does not - and if I brake only the right one brakes. If I put my turn signal on (either right or left, doesn’t matter), both lights begin to blink (because the hazards are on). If I then step on the brakes, both lights go solid. If I have one of the turn signals on, and I press the brake, both signals work (one turn, one brake). If I turn my running lights on (half pull on the light stick), both of the turn/brake/hazards lights turn on. But, the hazards won’t work, the brake lights won’t work, and the right turn signal won’t work. I tried replacing the flasher relay, but that didn’t seem to change anything. so I went back to the old one… I’ve attached the wiring diagrams and a photo of my lights. the bottom light is the backup light (never works), the side is a running light (which goes on when I pull the stick half/full) and the top right is the hazard/brake/turn.

Thanks for any/all advice

I have an 85 Chevy Silverado with a 6.2l diesel…

the links are just to the images incase the images don’t work

I would first suspect the light bulb sockets or a few of them. They are cheaply made and perhaps not grounding properly. When one light doesn’t work and then works later when something else is on it may at that time share the ground. If this vehicle uses the old style 1147 1157 bulbs then it is very likely one or two sockets are not grounding well. Don’t need to trace ground wires or the harnesses you can just solder wire to the ground portion of both brake light sockets and attach the other end of each wire to a good ground (clean metal with a sheet metal screw) and if the brake lights then work you know your problem is failed socket grounding. I have seen and repaired this sort of problem before and the first time I was confronted with it it was confounding as the grounds looked and tested okay but I guess they weren’t okay enough!

Thanks for the suggestion! I’ll try grounding the socket to the chassis (sand off a tiny bit of paint and hopefully find a hole so I don’t have to drill through the frame).

ended up being the turn signal switch. what a pain to change!

Oh my. Wish it could have been anything but that. Well, at least you got it pinpointed. Best of luck.

Even though replacing the switch cleared the problem I suggest you clean the battery to chassis ground connection.

If you have trailer wiring, I suggest that you get it inspected, and also inspect the wiring harness on any trailers that you own or pull. A lot of these problems begin there.