Hey guys, 2003 F-150 Tow Package. I hooked up my friend's trailer (small snowmobile trailer) and connected the 4-prong light plug. The brakes and signals work but the running lights don't work. I know they are good on the trailer so the issue is on my truck. Suggestions on what to check? Thanks!

 

Your fuses.

 

With the integrity of todays vehicles, wrapped factory tow wiring harnesses that are fused and relayed... the chances of it being anyithing other than a fuse on a newer truck is slim/remote/unheard of.

Unless of course there has been somebody messing with your factory wiring or you have been involved in an accident that messed something up.

Trailers on the other hand are notorious for poor workmenship. I have seen new trailers that needed wiring repairs after being delived from the factory. In fact I fix about 20 of these a week from various manufacturers. I guess that is what happens when you hire someone who works for minimum wage and doesn't speak the language....electricity.

If you have a trailer related fuse blown in a tow vehicle keep in mind that something blew that fuse... and it was most likely due to the trailer wiring problem; not the tow vehicle.

So, the trailer probably needs to be looked at too.

 

You guys are great, I love this site! That's good info there Colorado, I believe it. I did have to replace the trailer wiring receptacle piece that bolts onto the bumper last year because it got bent when my dad backed my truck into a snowbank. I replaced it and everything worked well so I was pretty sure that wasn't it. I just checked under the hood and Fuse #5 is blown, a 20A yellow fuse that has to do with trailer wiring. I don't know what blew it but I'll get a few for spares. Thanks again!