I have a 1999 F150 with the 9 pin connector for my trailer I plugged my trailer in today and the lights came on for a little while then quit working my blinkers and brake lights work fine just no lights?? I checked fuses and didn't find any bad ones I cleaned the connections and checked the trailer with a different truck and the trailer lights work fine! so what am I missing???

 

Sorry 7 pin connector all fuses are good and I swapped relays around still no lights the lights on the truck work but not getting any power to the pin on the trailer connector??

 

Just to clarify:

When you say you are not getting any power to the pin on the trailer connector you are checking that with a test light or multi meter; correct?

 

You probably have a poor ground as they originally worked and went out. Circuit resistance increased with poor ground/connection. Double check all your connections at the rear of the truck for a bad one. Possibly even a leaking lense letting water/moisture in. Remove the assemblies and search.

 

I had the exact same problem last week. It ended up being one of the fuses under the hood. I don't remember which one though. The description in the owners manual was kinda not real clear though I remember. You could pull the fuses under the hood one at a time to see which one is blown and that will probably be the one that will fix it.

 

fuses for trailer lights and not same fuse as truck taillights. look up the fuse number in your book. Make sure yoy have a good ground on the truck wireing.

 

https://www.fleet.ford.com/maintenan...ls/default.asp

 

The under the bumper 7 pin socket is famous for a bad ground connection, Check the large white wire connection on the back of the socket. If you suspect a bad ground, use a jumper cable from the truck frame to the trailer frame, see if that makes a difference.

This ground problem usually shows itself if you have a lot of rain, or go through a car wash, just before hooking up the trailer. The factory socket can trap and hold water for quite a while.

Easiest way to test the truck socket is with a trailer emulator. It's a LED test plug, that simulates the male end of the connection. They are about $25.00 at trailer/RV parts places.

Dave

 

Both test light and multi meter

 

well I checked every fuse in the cab and under the hood they were all good checked the voltage on fuse #201 for trailer running lights it was at 12V so I checked the ground out back it was good but I cleaned it up on the inside of the frame where it attaches to the frame! I then checked the power at the plug connection before the rear spit for the tail lights and found it still had power then check the wire about 3 inches before the 7 pin connector and had power there but nothing on the pin so I pulled out the pin and found the wire was bad going into the pin so I cut the bad part of the wire then soddered it back together and now they work fine thanks for the help!

 

Elbow grease and deductive reasoning. Good Job. You can always put a new one on now that you know it works, when it feels good to you.