Electrical Short

Tiny
PROFESSIONALGRADE
  • MEMBER
  • 1993 GMC SIERRA
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
Hello first time forum user. Ok, so on my truck I repeatedly have my parking light circuit fuse blow when I have a trailer hooked up. I first thought the problem was the trailer, but since it has been the issue with multiple trailers attached I have decided the problem is in the truck. I read a post here about using spade connectors and leads to a working brake light fixture. I connected it to inside cab fuse panel in place of the "#9 fuse, (20A) Parking lamp". As expected the light came on with the switch. (Side note all test to this point have been done without trailer attached) I visually inspected wiring from 3&1 4pin trailer pigtail to the RV type plug where it piggybacks off of. No visual damage. My connections at the 4pin are soldered heat shrinked. Wire bundle is electrical tape wrapped. Disassembled RV plug and found it full of dirt from years of dirt road living and being primary means of hauling, launching and loading jet skis. Removed the core, cleaned contacts and corrosion from exposed wire tips. Replaced. No change in problem as soon as got dark turned on lights and blew said fuse. Next I disconnected rear lights at their factory connectors with no change in light intensity from installed test light. Visual inspection and wiggling wire bundle from rear to front found no issues and no change in light intensity. Under dash wiggled fuse panel and wires behind no indication of change from light. Visual and wiggled wires from firewall fwd nothing. Checked light connections nothing. Pulled cluster trim panel AHH HA a mickey mouse plastic quick splice with a female spade connector pluged into the brown wire unhooked this single white wire and no change. Turned off the headlight/parkinglight switch slammed the door kicked the tire called it dirty names and checked again. Nope. I'm out of ideas. Thank you in advance for any assistance.
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Wednesday, May 4th, 2016 AT 12:45 PM

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Tiny
HMAC300
  • MECHANIC
  • 48,606 POSTS
Get yourself a circuit breaker to put in place of fuse in dash for lights. Then it will click and come back on so you can check this. Then start at the firewall on the brown wire as that powers the lights. Then check to make sure you have a good ground to trailer lights and truck the truck ground is normally on lh frame rail at back but could be on trailer hitch. Make sure ground wire leading to trailer is a good connection as well. You might try running a compass along the wire bundle if there is a short it will go screwy so you can check at that point. It doesn't need to be a good compass. Do testing with trailer/s disconnected if no problem then it's a trailer problem either on ground circuit to trailer or wiring, Normally in lights as they can fill with water.
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Wednesday, May 4th, 2016 AT 1:00 PM

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