Trailer Tow Package Problem

[01SMOKINSD]

Not sure where to put this but here goes. My brother was using my truck a few weeks back to tow an encolsed trailer when he discovered he had no marker lights on the trailer. Turn and brake lamps worked fine though. For the last two weeks now I have been trying to trace down the source of my problem. About a month ago I added the lil red light bar under the tailgate that comes stock from ford on the dual wheel trucks. I didnt but this from ford so I spliced into the trailer tow harness for the ground and power source. This light also has quit working. I have check the fuse for these lights, according to the manual, in the box under the hood. The fuse is good and I have power innto and out of the fuse, but no power to the rear of the truck. My question is, does anyone know if this power sorce is run through a relay somewhere that may have shorted out and Im not aware of. I am trying to avoid pulling the entire harness out of the frame rail to look for a short in the wire. I have a hard time believeing that the lil lights I installed would have pulled enough juice to burned the wiring. Any help would be appreciated. Thanks!

[mschn99]

look in your manual again. there are, i beleave two seperate fuses and tow seperate relays that the trailer wiring is powered up by. id have to do more research know which ones they are, let me know if you cant find them........

[01SMOKINSD]

I knew that there were two relays that are under the hood located next to the distribution box but there is no mention of them in the manual nor are they labeled under the hood. Im pretty sure they are the ones that you have to install when you purchase the truck to have the trailer wiring work in the rear of the truck. I will swap them out today when I get home. Do you think it is possible that the 3 lil lights I added could have cooked the relay or is it just ironic that it happened. The lights worked fine for over a month. Thanks for your time and help Marc.

[mschn99]

you need to look in your manual for the trailer running lamp fuse and trailer running lamp relay, they should be there.......i think its gonna be fuse 4 under the hood and then one of those two in the relay block......

[01SMOKINSD]

According to the manual, the running lamp fuse is #8 under the hood. I will check #4 though. I changed all 4 relays yesterday under the hood, but that didnt work. Its starting to look like im going to have to pull that darn harness and start tracing the wire. Thanks for all your help. I know that when I find the problem it's going to be something stupid that I over looked, LOL, never fails. Thanks again.

[payableondeath6]

not that this was on a SD but on my F150 i had a heck of a time getting the trailer lights to work...checked all fuses, checked all relays, checked all the wiring (both truck and trailer), bought a new tow package harness...still no lights...well come to find out it was a bad fuse in a fuse box that neither the haynes or owners manual listed as being there. so i guess what i'm trying to say is it sounds kinda like a bad fuse and i'd start looking for boxes that shouldn't be there

[01SMOKINSD]

Payable...I thought it was a fuse too, but I cant seem to find a blown one. Do you remember where the fuse was located on your F-150? Possible that there is one on the SD as well. I really dont want to pull the wiring harness unless I absolutly have to. Im almost positive that there has to be a blown fuse somewhere, just cant seem to find where it is.

[payableondeath6]

the fuse box i found was in the engine compartment behind the relay box...it was unlabeled and was actually electrical taped shut from the factory (so it looked). i found all this info on the internet (don't remember where) so that's how i knew.

[Banshee34]

I've got the manual in electronic format... if ya want I can forward it to you if you have an e-mail account that will accept large files....

Just let me know!

[harald@bd]

it's been a while guys but i would swear that there is a sepate fuse under the dash that controls the parking lights .this is over and above the trailer light control under hood. I would bet thats the problem cause it happened to me.