Trailer light problems

[SDChris]

Hey everyone, I am having an issue with my trailer lights not working. I tested the plug on the truck and nothing. The wiring looks good (no visible signs of damage). I have looked at the manual and it shows 2 relays in the cab fuse box one for each side of the trailer. How do you test the relays, and is there any other fuses for these lights that I am not aware of? Thank you for the help.

2008 F250, ext cab, 4x4

 

[BIG JOE]

With a 12v test light.. ground it.. then check for power by testing/probing each side of the relay(s). If the light lights after probing both sides.. Relay is good. Same with fuses.

Yes there can be other relays & fuses. Some under the dash... some in the PDB, under the hood. Can't help you there.. as they are Year/Model/equipment package specific. Check your Owners Manual.. or maybe someone with an 08 like yours will Chime-In ????

Joe

 

[DaveBen]

The owners manual will show you ALL of the relays and where they are. None are hidden. Make sure your ground connections are good. Some lights use the trailer ball for a ground, so it must be clean and oil free. Good luck!

Dave

 

[SDChris]

Thanx Dave and Joe. I found the problem there was a 25A fuse blown under the hood and one in the cab. There are 3 or 4 fuses and 2 or three relays for the trailer lights. When I found the one blown under the hood I replaced it but still didn't have any lights so I dug a little deeper and found the one in the cab.

 

[SDChris]

I had no idea some lights ground on the ball good to know, when I tested them I used the 4 wire ground because it was the easiest to get to, but I will definitely double check the ball next time before chasing fuses.

 

[DaveBen]

The trailer lights can ground through the trailer ball. A better solution is the fourth wire in the connector. It is a ground wire. The 7 pin connector has grounds also. Glad you found the problem.

Dave

 

[Shaggy]

I had no idea some lights ground on the ball good to know, when I tested them I used the 4 wire ground because it was the easiest to get to, but I will definitely double check the ball next time before chasing fuses.

Still working out for you?

 

[BIG JOE]

I had no idea some lights ground on the ball good to know, when I tested them I used the 4 wire ground because it was the easiest to get to, but I will definitely double check the ball next time before chasing fuses.

And FWIW (All ?) There's a Diagram/Legend embossed on the lid/cover of the trucks 7 pin plug-in, showing you which pin powers what, w/ground identified. (Good place to trouble-shoot from ?)

Joe

 

[SDChris]

I had two fuses blown, one in the cab and one under the hood. They have been working fine, I pulled a trailer all last weekend with no problems (fingers crossed).

There is a diagram on the cover of the 7pin but it was a little harder to get my tester clamp in there so I used the 4pin ground, but I will double check the ball for ground next time.

2008 F250, 4x4, ext cab.

 

[DaveBen]

The trailer ball is physically bolted to the frame (ground), so the ball is ground. You can test it all day.

Dave