99 f250 4x4 psd


Trailer blinkers and brake lights work fine but the tail lights and side marker lights don't work. Everything works on the truck. This trailer is just a small 4'x8' that uses the "flat four" plug. No tail light power at the plug, also no power to the tail lights at the 7 pin plug. I checked all the fuses and followed the tail light power wire half way up the frame rail and it's dead.

This wouldn't have a relay for just the trailer tail lights would it?

Any ideas on what the problem might be would really be helpfull. Thanks

 

I had a trailer light issue once and it turned out to be a fuse in the power distribution block under the hood.

 

Has it ever worked? When I first got my 99, it was missing a couple of relays under the hood.
Check the owners manual, it should tell you what fuses and/or relays are used for the
trailer brake and running lamps.

If you don't have an owners manual, go to https://myford.fordvehicles.com/ and signup and enter
your VIN, then you should be able to get a PDF of the owners manual from the DOWNLOADS drop-down on the
left side of the screen...

 

I'm embarrassed to say I never even knew that fuse block was there! Guess what I found a blown 15 amp fuse. Don't have any spares right now but I'm sure that's the one since everything else works.



BTW, between the master cylinder reservoir and the power distribution box I found a small relay box that holds two large relays but they are gone.



Anybody know what they would be for? Thanks again.

 

Just saw this after my last post, the link didn't work for me. I'll save it and see if it comes up later. Oh yeah the lights worked 3 months ago.

 

I blew a fuze for the power point, took a week to find out that the cigarette lighter fuze in in the underdash fuze panel, and the power point fuze is under the hood.

On the other hand, they sure did do a fine job of designing the light switch. LOL

 

Replaced that fuse, did the trick, thanks.

 

No problem, that's what we're here for.