# Trailer Wiring Question For Chevy/gmc 2500 Hd



## GoVols

I could use the help of some 2500HD Duramax owners. My new 07 Classic 2500HD did not come with the OEM HD Trailering package. In a good sense, that made ordering a Putnam hitch for it very easy, but the wiring is giving me some pause.

I kept my Prodigy and the GM wiring harness from my '06 1500, and plugging that in won't be a problem. I have already bought a pigtail/vehicle-end 7 pin receptacle to plug in the back too. What I'm confused about is what needs to happen in the fuse block under the hood. The fuse block is different for the two-battery diesels than my 1500. I would assume I need to put a ___? amp fuse in the STUD #1 location, and there already is a 30A fuse in STUD #2. I want to be sure I have a working charge line back to the 7 pin connector as well as power to the trailer brakes.

What, if anything, needs to go in STUD #1, STUD #2? Is there a wire or jumper I need to connect and/or run for the 12V charge line?


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## California Jim

Here's what happened on my 07 Burb which may be similar if not exact.

You are right in that the positions labeled "Stud #1" and "Stud #2" are the two circuits that need to be energized. There should be a 40amp fuse in #1 and a 30 in #2. Check your fuse list to confirm this as I may recall this backwards.

Then you still need to connect the circuit wires to the under-hood fuse box. One wire is about 12" below the master cylinder and the other is hiding on the driver's fender well behind the fuse box. Both wires are coiled and taped to the wiring harness. You will know how to connect the wires to the proper stud buy the size hole in the connector blade at each wire end. One is larger than the other to fit on the larger stud.

For more info about this click HERE for my experience with this.

Good Luck


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## GoVols

California Jim said:


> Both wires are coiled and taped to the wiring harness.


Those wires run back to the back end with the trailer wiring bundle already there?


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## California Jim

Believe it or not, this is how my Burb "with" the tow package came from GM.







Yes, at least one of them (electric brake voltage) runs to the back 7 pin plug. I believe the other is the charging circuit and also runs to the 7pin.


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## map guy

These two GM publications should get you going..... A wealth of information is available on this website if you understand technical documents

Classic K PDF 1 See page SP-26.

2003 & Beyond Classic Electrical PDF See page A-20

Web site front door:
GM Upfitter Website 

Map Guy


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## GoVols

Thanks Jim and Map Guy. I pulled the case up on the engine compartment fuse block enough to see that wires, both red, were terminated on the #1 and #2 studs already. Looks like they are already in place.







Only Stud #1 is missing a maxi-fuse. This seems to correspond to the information Map Guy pointed me to on the GM Upfitter website (missing the Stud #1 maxi fuse and having a 30A in place at Stud #2).

I'll work on installing the controller and the 7 pin receptacle this weekend. I ordered a pigtail/receptacle from etrailer.com, so I hope it will just plug right into the terminated and capped wires at the back of the truck.

JT


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## NJMikeC

You have the '07 Classic. Doesn't it have the old style normal plug which is underneath the dash board? They made this change because of the integrated brake controller which is on the "new 07's and not the Classics.

Mike C


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