1999 GMC C1500 ATC fuse keeps blowing

Tiny
STURGIS
  • MEMBER
  • 1999 GMC C1500
  • V8
  • 4WD
  • AUTOMATIC
  • 183,500 MILES
My sons ATC fuse under the hood keeps blowing. It is usually a 20 amp fuse. I put a 30 amp fuse in it as that is all I had handy, it worked a few days and then that one blew too. I unhooked the actuator and the push button 4 wheel drive selector and tried to put a 20 amp fuse in it and it blew that right away. I did this with about 5 more 20 amp fuses and it did it to every single one of them. If I put a 30 amp fuse in it it won't blow it right away, but I am thinking it will blow it in the next few days as we have to use 4 wheel drive everyday to get out of our driveway.

I unhooked the actuator and the push button selector to go thru the process of elimination but since it blew the fuse with them both unplugged I am stumped.

Any help would be appreciated. I really don't want to go chasing wires, but if I have to I will.
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Thursday, February 11th, 2010 AT 5:33 PM

3 Replies

Tiny
FACTORYJACK
  • EXPERT
I looked on GM service information, and for a 99 GMC K1500, there are no transfer case or 4WD fuses in the underhood fuse block. I don't even show an ATC fuse. It is somewhat rare, but not uncommon for SI to be incorrect, but it is to early to tell. Verify the info, and possibly include the last eight of the VIN. I take that back, I look on ALLDATA and it shows an ATC fuse underhood. It looks like it feeds power to the encoder motor, and the transfer case control module. You said you disconnected the switch, and actuator. By actuator, do you mean the front axle actuator, or the encoder motor on the transfer case? If you disconnected the encoder motor, just disconnect the ATC module and see if it blows, if so you have a short to ground. If it don't blow, chances are good you have a shorted encoder motor. The module is shown to be under the dash, by the steering column.
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Friday, February 12th, 2010 AT 11:56 PM
Tiny
STURGIS
  • MEMBER
I unhooked the actuator from the front differential and also I unhooked the wire harness from the back of the push button 4 wheel drive from the dash. When I did this I was still blowing the 20 amp fuse as soon as I made contact with the fuse blades. The 30 amp fuse won't blow like the 20 amp does, but over time it has blown within a weeks time of installing it.

What does the ATC module look like?

So you think it is either the ATC module or the encoder motor?
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Sunday, February 14th, 2010 AT 1:30 PM
Tiny
FACTORYJACK
  • EXPERT
Those are the only two items that the ATC fuse supplies power to. My guess is the encoder motor. It could have fluid that leaked into it from the case causing it to short. The 30 amp fuse is not blowing as quickly because it is able to handle more current. The problem with this is that you run the risk of damaging something else by installing a larger fuse. Potentially damaging wiring, or other components.
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Monday, February 15th, 2010 AT 10:18 AM

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