vahokie

Recently found that my trailer running lights aren't working. Turn signals and brake lights work. I pulled the #10 fuse, which is supposed to be a 20a fuse, and found that the previous owner had put in a 15a, but it wasn't blown. Swapped the relay with the fog lamp relay (R201 & 202) and still nothing. I've found some wire splicing done by the old owner near where the trailer wire bundle comes into the wire chase below the driver's door, but there's so much stuff in there it's hard to tell what's what.

My harness looked corroded, so I even tapped into the running lights just behind the harness and still nothing. I was going to check my 7pin to if i had any there, but I was going to get a new multimeter (my cheap one doesn't seem to be working properly) and test that one before I took the wiring wrap apart.

It seems like I have a broken wire between the fuse box and the harnesses. Does anyone have any other suggestions before I start looking for a broken wire? This stuff isn't completely new to me, but I by no means am I a pro.

Thanks in advance!

It's an 04 FX4 with both 4 and 7pin harnesses.

bubbabud

I have found the best way to check this is with just a cheap test light looks like a ice pick with a light in the handle and a ground wire you can just pierce the wires start at the fuse and work back. Did you power up the trailer its self to make sure the problem isnt in the trailer wireing or just bad bulbs?

dykzeulb

iTrader: (1)

Also a possibility of the trailer not grounding out. My trailer running lights didnt work on my brand new 2010...or my new silverado I bought, not sure on my King Ranch. Like he said your best bet is to just stab the wiring harness from back to front, or front to back. its fairly easy to trace, ecspecailly if you have access to a lift. Then just tape up each spot where you did it, or use "Liquid Elecrtical tape" (more water proof). Just dont butcher your stock harness, or you will really be up a creek!

vahokie

thanks for the help. yea i agree. it actually is a tailgate light bar that I hard wired into the 4 pin harness that lead me to find out they weren't working. i was planning on getting some wire and just doing a quick tap into my license plate or tail light running light to make sure the bar is working. then i was going to take your advice and work down the wire to see if i can find a break in the wire - i just need to get some better testing equipment.

I feel like i can get the bar to work one way or the other, but i wanted to make sure i can get my harnesses working.

thanks

vahokie

it's been a while but I eventually went to Recon and sent them a picture of the bar with 3 lights not working. They sent me a new one right away. Now, I've installed the 2nd and the running lights won't come on. I've checked my trailer wiring with a voltmeter and know that my truck's wiring is good. Email recon and they said i needed to add resistor's to get it to work w/ running lights. Well....I'm not going for that. I think i got another defective bar. Yea maybe the resistors would get it working but i don't feel that i should have to. Has anyone ever had this problem and was able to fix it by adding a resistor? They came back with a really crappy response on how to fix it so I'm a little POed now and im going to try getting another bar or my money back.

Any advice on fixing it with a resistor would be appreciated. Thanks.

biggin86

I don't know about your light bar but when I installed mine it required a 12V source for lights to work properly. I had tapped into what was supposed to be the 12V wire on 7 pin but no power. Turns out that there was no relay to supply power to it. Bought a relay, put it in place and the lights started to work.

rmilman

Just noticed that my trailer running lights aren't working. Here's the strange part. They were working when I was hooking it up and had the driver door open. When I closed it and was driving down the road they shut off. All the other lights are working fine. Tested by opening the driver door again, sure enough they turned back on. Closed the door and after a few minutes they turned off again. Is there a relay with a timer somewhere that might be hooked up wrong? I don't know what the door has to do with it unless it's tied to the cargo light somehow. Anyone have an idea where to start looking. All the fuses and relays seem to be in working fine and none are missing.

lariatboy

Sounds like you have some wires crossed somewhere along the line. If you just turn on your cargo lights without opening the door, and the running lights come on on your trailer, then yes, it would appear you're tapped into the accessory light circuit as opposed to the running lights circuit.

Jan Bartos

Hey Man, I had the same problem on my 2010 F150 Lariat. Trust me, it is just one of the fuses. No big deal at all.

This website http://thetransmissiondoctors.com/bl...ights-failure/ actually describes the problem well and shows which fuse to replace. Good luck.

canadian80

so ive got the 2010 king ranch ...my trailer lights only have running lights.my truck has running lights signal and break lights.ive changed out the one fuse it was #31 it was blown..is there any other fuse that it may be? ...relays are working just cant seem to find the fuse for signal and breaks lights for the trailer.been threw the fuse box a few times and have found nothing.all the wires on the trailer are new and work find on my car just wont work on my truck. any ideas?