I was rewiring my trailer lights and had power to the + and - posts where you plug your trailer lights into the truck below the bumper. I heard some sparking and now I don't have any power to the + or - posts. All the other clearance lights, turn signals, brakes, flashers work/their respective posts. Is there a fuse somewhere for just the + and - posts (I think these are supposed to always be hot to run equipment in your trailer/charge the trailer batteries???) I can't find a fuse for this, which I think I must have blown; I used to have power there, now I don't, no matter what I do. Please help!!!

I think the fuse for the 'Battery' position on the 7 wire connector is in the fuse box in the engine compartment. It would be in the top left side of the fuse's and it's the bigger square type, either 35 or 45 amp.

Which one exactly is it? I can't find anything labeled that directs me to a certain fuse. Do you think it is one of the smaller square top fuses that you can see down into. Or is it one of the huge black fuses. I still can't find it. All the fuses I checked appear to be fine. Any other input?

It will be the one that is on the very front passanger side corner. It is probably covered by a label and might have a shunt in place of the fuse. In that case you need to replace the shunt with a fuse.

I believe it is stud #1

If you are looking over the fender on the driverside into the engine compartment it is the square fuse in the upper left corner of the fuse compartment. If that fuse is OK , check, with the key on, if the Battery/Black connector in the 7 wire connector on the truck is hot(use a test light). That prong is about 1 o'clock. If it's hot, then the problem is in the trailer wiring or trailer connector.

Ok, I'm printing all of your replies and am going out to the garage now to see what I find. I'll let you know soon. Thanks!

Alright, I found which fuse and slot it is. Hopefully I will be able to post a pic that I took to show exactly which one. It is the very forward and passenger side fuse of the whole fuse box in the engine compartment, like most of you said. My question is, what the heck is the red looking non-fuse thing in that position? I think Max Power called it a shunt. I don't assume that it allows power to be run through it, but I am almost 100% certain that I had power to the + terminal in my trailer plug, then all of a sudden I didn't. If this is truly just a cap/cover for that "Stud 1" fuse slot, then how did I get power earlier, then none at all? Is a shunt just a dead end cap/cover for that slot? If so, why did I have power berfore or am I smoking crack? Also, are the square see-thru-top fuses in the other slots GM fuses or can you get then at any auto store? I don't recall ever seeing those type before. I pulled another fuse and put it in the "Slot 1" that I am talking about and got power to the trailer plug that I was missing before! Next question is what size fuse should I replace the shunt with? This line is actually just charging a single 12v battery on a cargo trailer to have flood lights on the side of the trailer when not hooked up to the truck. I wonder why they have a shunt in that slot to begin with and not a fuse? Feedback on where I can get that fuse would be great?

That's the right one. I put in a 35 amp but was told I could use a 45 amp. Those fuses are available at any auto parts store, about $3.50 ea. Don't know how you had power to that pin without a fuse in that position.

So I'm right in thinking that I should never of had power to that fuse/trailer post. Meaning that the red think is truly a "no fuse"? I don't know, I could be wrong, but I thought I had juice earlier in the day. Thanks for you help. I run down to Wally World tonight of in the morning. Thanks again!

I think the fuse for the 'Battery' position on the 7 wire connector is in the fuse box in the engine compartment. It would be in the top left side of the fuse's and it's the bigger square type, either 35 or 45 amp.
It's a Green 40 amp fuse.

So looking on page 5-125 of the Owners Manual, Stud #1, it says "Auxillary Power (Single Battery and Diesels Only)/Dual Battery (TP2) Do not install fuse" So is it ok to install the fuse? Why wouldn't they want you to install one? And why didn't it come with a fuse to begin with?

So I'm right in thinking that I should never of had power to that fuse/trailer post. Meaning that the red think is truly a "no fuse"? I don't know, I could be wrong, but I thought I had juice earlier in the day. Thanks for you help. I run down to Wally World tonight of in the morning. Thanks again!

As info. The smaller, "see through" fuses are available just about anywhere, including WalMart. When I needed the bigger square ones, I went to Napa.

So looking on page 5-125 of the Owners Manual, Stud #1, it says "Auxillary Power (Single Battery and Diesels Only)/Dual Battery (TP2) Do not install fuse" So is it ok to install the fuse?

Your a Diesel, install the Fuse if you want Power at the 7 pin receptical.

Why wouldn't they want you to install one? And why didn't it come with a fuse to begin with?

If you don't Tow, you would not need it.



It's a 40 a fuse.

Idahofox

Thank you all! I got one of the green 40 amp fuses and everything works great now. Thanks again.

The red plastic thing you took out is not a fuse and cannot pass electricity through it, it's just a plug to protect that space. I got my fuse at a regular auto parts store, I guess Wally might have them but I wouldn't bet on it. I tried the auto section of a Ace hardware , they had lots of fuses but not that kind.

My fuse came with the truck but it was not installed. I had the red "plastic johnson" in mine also. Under the rear seat in my truck there was the trailer brake harness, 7-4 pin adaptor and the proper fuse all together in a bundle with tape wrapped around it. I have the 3500 dually but I imagine it's in yours also if you have the tow package.

Ya, Wal-Mart didn't have the fuse, but Checker Auto Parts did. I may have the fuse in my camper harness, I just haven't opened it up yet.