2001 Dually, Turn Signal Wiring Issues

Discussion in 'GM Electrical Tech' started by ASK, Sep 16, 2011.

  1. ASK

    ASK New Member

    I have replaced the multifunction switch, the flasher relay and all the right side lamps. Everything worked good for 2 weeks and then the right side fuse blows again when signaling a right turn. I am totally without thoughts of how to chase down the problem. I went to JustAnswer and was told to replace the multifunction switch which did not solve the problem. This is an 01 Chevy C3500, very clean, no off roading, never damaged, all under body wiring appears undamaged, with 104,000 miles.

    Anyone have the wiring routing for this truck? There is a fuse terminal on the inside drivers side that has a 20amp fuse that blows. The other fuse terminal under the hood on the driver side has 10amp fuses for the left and right sides. These have never blown, only the 20amp inside the drivers door. I have disconnected the lamp socket and isolated the wiring thinking the problem was in the socket. That did not "solve" the problem. With the socket wires disconnected the flasher would click really fast, as if a lamp was out, then blow the 20amp fuse.

    I think I could trace the wiring to see if there was a rub or grounded dark blue wire for the right turn signal if I knew where the wiring runs from the relay and how it goes thru the body to get to the various right side lamps. I have tried chasing it form the rear forward and get only so far and then things get really bunched up and I am not sure what to pull apart to look.

    ANY suggestions or ideas or experiences with this type problem? I would sure appreciate any help or thoughts out there.
  2. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    Stupid question, but does the truck have a non-factory trailer wiring harness? If so, I'd disconnect it and see if the problem persists.
  3. ASK

    ASK New Member

    The truck had the wiring and trailer tow package installed from the factory or from the dealer. It was new when I got it. All the trailer wiring is with connector clips. There are even separate fuses in the underhood fuse terminals marked trailer left and right. Non of those fuses have ever blown. It acts like a dead short on the dark blue, right turn signal, wire. I will crawl under it tomorrow and start taking the wiring harnesses apart to see if I can track it down. The wires are taped at all the splits and then put into plastic harnass covers. Looks very neat but obviously did not prevent this problem.

    Any other suggestions or comments would be welcomed.
  4. ASK

    ASK New Member

    Grounded wiring, problem found & solved

    Everyone with a GM truck should look under the driver side dash, just above the left side of the floorboard, where there is a wire terminal box that is attached with a 1 inch or so tall plastic nut and remove that cover. After removing the nut, compress the two locking tabs on the sides near the top and rotate the top of the terminal block towards you. The bottom has tabs that can then be lifted out and terminal block can then be pulled forward out of the way.

    Behind this terminal block is the wire bundle that goes from the driver side interior fuse terminal thru the firewall to the underhood fuse terminal. This wire bundle is probably an inch or so in diameter. It has a plastic type wire loom around most of it EXCEPT for the last 5 or 6 inches where it goes thru the firewall. There is a rubber type seal thru the firewall. The parking brake mechanism has an internal spring that has a STEEL HOOK that penetrates thru the steel housing. This spring end is slightly flattened for strength and produces a nice EDGE that can CUT THRU the tape only wrap on the wire bundle. In my case it was the DARK BLUE right turn signal wire that was RUBBED THRU and finally WENT TO GROUND.

    After isolating this wire bundle, I installed a new 20amp fuse in the TURN SIGNAL drivers side fuse block and tried the right turn signals and the hazard flasher. I was satisfied that this was the problem and the solution. I took a 2 inch length of radiator hose and split it length wise, placed it over the wire bundle and tywrapped it. This wire bundle can "move around" during normal driving and it took 10 years to finally rub thru. After many false alarms and blown fuses I finally found the cause and everything now works fine again.

    Anyone having any type INTERMITTENT fuse blowing or failure of some other type electrical parts should FIRST LOOK AT THIS AREA as the possible source. I could have saved the cost of a multifunction switch, several relays and flashers and a whole bunch of fuses along with about 12 hours of time and frustration.
  5. chevyloverss

    chevyloverss Member

    Hi there im reading your post and wanted to thank you for this usefull info as im gona look into this harnes and see if my issue lies therein. Well i hope so anyway but this is whats goin on with my truck, an 03 tahoe LT by the way. When my headlights are on and i put on my right side signal the high beams go on then off as i turn off the signal, if the headlights are off the signal works fine and this only happens with pass side, lol
    Last edited: Feb 29, 2012

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