Pics too if you figure it out, please.
Strange electrical issue.
- Thread starter Partsguy61
- Start date
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alpha_omega
Full Access Member
Did you check the trailer harness? The same principles apply here regarding feedback and tapping into lines. Have you pulled the battery cable and adjusted it to ensure it’s making full contact and/or the crimp fitting is secure. It may look that way, but it can be loose. Same goes for the body grounds. They may look clean and secure but until you remove them and clean them with a wire wheel you won’t know for sure.
Also if you haven’t already, pull the bulbs, make sure they have a small amount of dielectric grease and firmly reseat them.
Also if you haven’t already, pull the bulbs, make sure they have a small amount of dielectric grease and firmly reseat them.
When doing inspections of the battery cables, make sure they are not swollen near the battery attachment area. That indicates corrosion inside the insulation, crawling down the cable from the battery and creating too much resistance to electrical flow. Check cleanliness and connection from one end of cables to the other.
OP
OP
Partsguy61
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Yes, the 3rd brake light illuminates as well.
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Partsguy61
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I'm checking that tomorrow after work. I'm putting it up on a lift and dropping the spare tire. As for the body ground, I removed it and sanded both surfaces before reattaching it. The battery cables have been replaced the last time this happened and they are good and tight. I also removed the underhood fuse box to look for anything out of the ordinary and nothing appeared abnormal.
alpha_omega
Full Access Member
Did you check and clean up all of the grounds? There are multiple (three up front, one under the drivers side, two in the rear…).
alpha_omega
Full Access Member
Wait wait wait. I was curious if you mentioned whether or not these were aftermarket lights/bulbs or not so I went back and read your initial post.
Have you checked the wiring at the brake light switch?
ACDelco # D1539J
GM # 25981009
(It may be different for your year)
If everything else checks out and you haven’t checked the brake switch wiring and/or replaced this part yet I would suspect it might be at fault. This would also be the reason why your cruise control was acting up, since your cruise is directly effected by the brake.
Have you checked the wiring at the brake light switch?
ACDelco # D1539J
GM # 25981009
(It may be different for your year)
If everything else checks out and you haven’t checked the brake switch wiring and/or replaced this part yet I would suspect it might be at fault. This would also be the reason why your cruise control was acting up, since your cruise is directly effected by the brake.
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It sounds like a failing stop light switch to me, or a short in harness that connects to the stop light switch very close to the switch.
Both of those are cheap and easy, change the switch and look for rubbed wires on the connector before you plug it back in; if the problem persists then some of the more obscure things can be investigated.
Both of those are cheap and easy, change the switch and look for rubbed wires on the connector before you plug it back in; if the problem persists then some of the more obscure things can be investigated.
alpha_omega
Full Access Member
That’s the part and part number I suggested.
OP
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Partsguy61
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Yes. Brake light switch has been replaced with a GM part. If you disconnect the wiring from the switch, the brake lights still come on.
