99 gmt 800 lights acting weird help needed

[1997k1500Calvin]

I have a 1999 silverado 5.3, extended cab, 1500 z71. My problem is, brand lights and signals work fine by them selves.. if I use the brakes and the blinkers(either side) at the sane time they swap and my lights are dimmer tha. They should be. When the head lights are on its even worse, when braking my dash lights indicate blinkers are both on and all my lights (brake and blinkers) light up. Even my lights on ny tag light up in random ways. My reverse lights also don't work, I have checked all bulbs theyre all new and correct, ive replaced the brake pedal switch, relay for blinkers, and sanded and cleaned all the grounds.... whats next

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[BoxerPitMix]

I've ran into a few NBS trucks with similar problems, it is usually a bad ground. It sounds like you've checked that, though. But, I've also seen lights do some pretty crazy things like you're describing when the multi function switch goes bad.

Before I replaced that though, I'd first try pulling all of the fuses for your trailer lights under the hood and see if you still have a problem. If something is crossed out on your trailer plug or somewhere in that harness, that's an easy way to rule that out.
If that doesn't do anything, I'd try replacing the flasher module and see if that fixes it.

Do you have a power probe? If so, you could also pull one of your tail lights out and ground the (-) wire that goes to your turn signal. If you don't have one, strip back a section of the wire and run a good temp ground to your frame. Try everything then and see if that solves your problem. If they work correctly with that - you'll know for sure that you have a ground problem.

 

[1997k1500Calvin]

I've ran into a few NBS trucks with similar problems, it is usually a bad ground. It sounds like you've checked that, though. But, I've also seen lights do some pretty crazy things like you're describing when the multi function switch goes bad.

Before I replaced that though, I'd first try pulling all of the fuses for your trailer lights under the hood and see if you still have a problem. If something is crossed out on your trailer plug or somewhere in that harness, that's an easy way to rule that out.
If that doesn't do anything, I'd try replacing the flasher module and see if that fixes it.

Do you have a power probe? If so, you could also pull one of your tail lights out and ground the (-) wire that goes to your turn signal. If you don't have one, strip back a section of the wire and run a good temp ground to your frame. Try everything then and see if that solves your problem. If they work correctly with that - you'll know for sure that you have a ground problem.

I got the flasher module or relay already and replaced it, now the lights just dont flash as fast

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[1997k1500Calvin]

Ok.figured.out.my junction box under the bed of the truck had burnt up linking all the.lights together, 30$ later all my lights work great...!!

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