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Any/all help greatly appreciated.

Just changed tow vehicles from a 2001 Yukon to a 2004 Yukon XL2500.  My interior trailer lights worked fine before.  Now, no lights.

 I checked out the connector on the Yukon, and the pin that looks to be 12 volts hot,,,,,,,isn't.  I've checked all the fuses.  All check OK?

 Any ideas?

 TIA

At least in the 2500HD trucks, there is an underhood "square" fuse that you have to put in for that constant +12V to work.   The fuse is NOT installed from the factory, but is usually taped up with the OEM trailer brake controller harness pigtail (usually comes in the glovebox new).   

 So check the underhood fusebox, if a fuse is missing that is probably it...

Also, on my 02 F250, that circuit is only hot when the key is in the auxiliary or on position... We put a jumper in place of that relay. Check it with the truck on...

Tom

tholt29:

Also, on my 02 F250, that circuit is only hot when the key is in the auxiliary or on position... We put a jumper in place of that relay. Check it with the truck on...

Tom

 FYI, Ford makes it key-switched, GM makes it +12V all the time.

Impala SS AutoXer:

At least in the 2500HD trucks, there is an underhood "square" fuse that you have to put in for that constant +12V to work.   The fuse is NOT installed from the factory, but is usually taped up with the OEM trailer brake controller harness pigtail (usually comes in the glovebox new).   

 So check the underhood fusebox, if a fuse is missing that is probably it...

 

 I agree, when we switched from our 2001 1/2 ton Suburban to our 2005 3/4 ton Suburban, there was no change in how +12v line in the trailering wiring.  You do have to install the fuse mentioned above to make the wire hot, but we had to do that in '01 also. 

If I recall correctly though there is a difference in the brake controller harness pigtail so you can't use one from your earlier vehicle in the '04 without switching a couple of the wires around (let me know if you need those instructions, I think I still have them around somewhere), or use the one that came with the '04.  In my case I was reusing the brake controller so it was easier to switch the two wires around in the '01 pigtail than it was to rewire the controller to the '05 pigtail.

Thanks everyone.

The Yukon didn't come with the harness/fuse.  I hooked up my brake controller harness from the old Yukon, and it works perfectly.

I checked all the fuses under the hood, but didn't "add" a fuse.  BINGO........I hope!

Is this "square" fuse a relay?

Thanks again.

  

If I recall correctly though there is a difference in the brake controller harness pigtail so you can't use one from your earlier vehicle in the '04 without switching a couple of the wires around (let me know if you need those instructions, I think I still have them around somewhere), or use the one that came with the '04.  In my case I was reusing the brake controller so it was easier to switch the two wires around in the '01 pigtail than it was to rewire the controller to the '05 pigtail.

 Well, I think I located where the fuse goes.  It has a plastic plug that says B+ there now.  I need to put a meter to it and check it out.  Do you remember what the current rating on the fuse is?  There is mention of the fuse and harness in the owners manual, but absolutely no details!

 Now I'm a little concerned on the harness and controller.  When I changed vehicles, I also changed controllers.  I took the old harness and wired the new controller like the old one.  It has worked for a for 2 trips, but I did have one time on the last trip when it kind of flaked out for a while.  By chance do you have the color break outs still?

Thanks again!