Trailer Battery Not Charging Off Harness

[hogan521]

I have a 2002 GMC Sierra 1500 with the factory towing package and the factory 6-pin trailer wiring harness. When I hook up my camper to the harness the battery is not charging while in transit the way it should be. Usually by the time I get to my destination approx. 3hrs away, my camper is about 3/4 dead from running the fridge.

I had an Explorer previously that the camper dealer installed a wiring harness on and it worked fine, so I know its not the trailer. I talked to the service tech at the trailer dealership and he told me that even though the truck has a factory towing package, sometimes there is a fuse under the hood that is not installed from the factory that would be the connection to charge the trailer battery. I looked under the hood in the fuse panel, but the only open holes I see do not have connections to accept a fuse.

Can anyone help me track down this mysterious fuse? I don't want to have to pay for a service tech to put it in.

[Z15]

There is another fuse panel, drivers side of dash. Open door all the way, its on the side of dash facing the door. Don't have a clue if the fuse you seek is in there. Just traded away my 2004 GMC so I can't go look.

Also, did you check for a blown fuse in the under hood box?

Your owners manual should have this info?

[ltlieu]

i own a 2005 gmc sierra 2500,,,,,,,,,,,,,the fuse should have come with your trailering package at purchase,, it needs to be installed in order to charge battery during trailering. Location of fuse box should be in your manual.

[hogan521]

I checked all the fuses under the hood and none are blown. Looking through the manual I can only find the same generic description that the box itself gives. I think I'm just gonna break down and have them do it. I need it done by next Thursday and don't have alot of time between now and then.

Thanks for the suggestions

[jacob54904]

i have a 2001 gmc sierra 2500 hd. stock from the factory these trucks are set up for the accessory wire to charge the battery, but they are not hooked up. they never have been in the past either. there is a wiring harness you can buy and install to get this wire to work. there is no fuse for it in the fuse boxes. i am not sure where on your truck the harness installs but on mine it is next to the gas tank so it is kind of hard to get at. if you are up to it you could do what i plan on doing and just run a live wire right from the battery and connect to the correct wire on the trailer plug. if you decide to go this route then i would strongly suggest fusing this wire with a 40 to 80 amp fuse. i hope i helped some. good luck

[Z15]

I recall my 99, 01 and 04 all came with a jumper harness to use for trailering. It was in the glove box and I was told you needed to use that harness to have trailer brakes. I never used them and threw them in the glove box when I traded. The trucks all had the HD trailering option with the 6 pin connector at the back bumper.

If you bought the trucks used, the previous owner may have kept the harness or is was pillfered.

btw-My 2008 did not come with any jumper harness so it must be wired differently.

[jacob54904]

no i dont have a jumper harness, my trailer brakes do work tho, those come wired up already you just have to put the brake box in. i have talked to dealerships and all factory trailer harnesses come with three dead terminals on the trailer plug, the reverse lights, the electric brakes(because of the brake controller), and the accessory wire(which charges the trailer battery). again i would just run a live wire and be done with it.

[hogan521]

I did not use a jumper, just plugged the brake controller into the connector under the dash. I stopped by the camper dealership and told them my problem, they looked in the fuse box under the hood and determined that the required fuse was missing. They said it was common, that GM does not install it from the factory and if the truck was never used for that type of hauling it would never have been noticed. They put in a fuse (one of the larger ones on the edge of the box) and it has worked great ever since.

Thanks to everyone for your help.