1994 GMC Sierra Electrical

1994 GMC SIERRA
270,000 MILES • 4.3L • V6 • 2WD • AUTOMATIC
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CHAPAFM
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  • 3 POSTS
I recently removed the trailer wiring harness. Now the tail lights, license plate lights and backup lights do not work. Turn signals work correctly by themselves, if i step on the brake, turn on the parking or headlights, the turn signals start flashing really fast as if a bulb was out. I have replaced bulbs and circuit boards to no avail.
Feb 18, 2015 at 11:33 AM
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HMAC300
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  • 48,601 POSTS
ow was the trailer harness removed just cutting it? you may have a couple of wires touching recheck it and check ground at lh rear of frame
Feb 18, 2015 at 12:12 PM
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CHAPAFM
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It was a spliced in wiring harness. I put all the wires back together to the corresponding wires of the same color as in the wiring schematic.
Feb 18, 2015 at 12:39 PM
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HMAC300
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recheck your work if you did everything correctly it should not do what is going on recheck wires at circuit board make sure they are plugged into correct spots.
Feb 18, 2015 at 1:08 PM
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CHAPAFM
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I finally got all the rear lights to work. I found a ground wire that was cut, fixed it, working good. Another problem has come up. When I step on the brake, my high mount brake light does not come on, unless the interior dome light switch is in the on position. I also noticed if the truck is parked and I have the driver door open, the high mount brake light will work, with the interior dome light switch in the off position. Could this be the interior dome light switch is bad or the door contact switch?
Feb 19, 2015 at 9:25 AM
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HMAC300
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are you sure it's not the lights that are next to the high mount brake light? there may be a push button switch on dash to turn them off otherwise they should come on when you open the door. the high mount brake light is wired separately from the brake light switch check the ground from battery to body there should be one there an done from body to engine as well, usually on back of head pass side on V8's
Feb 19, 2015 at 9:34 AM