I have a 2006 F 150 XLT SCAB. It's factory equipped with the tow package and I've been having a problem with the trailer lamps. The left turn signal will not blink at the connector, this is with the 'flat4" connector. All the other lamps work. The round connector also has some issues, but I need to get the flat 4 working first. I believe that the trailer circuit is not connected directly to the tail lights but somewhere forward. Does anyone heave any advise or tricks on how to find this wiring fault? Thanks in advance, John

 

The connector is under the bed. Try using a meter to see if it's working under there before proceeding.

 

The trailer tow brake/turn signals are isolated from the rest of the truck by fuses in the under dash fuse box. This prevents a trailer wiring fault from taking out the truck's turn signals.

Fuse F36 is for the right trailer signal, F42 is for the left one. Check F42 first.

 

Thanks all, it was the fuse.

 

:thumbs-up