I have a 2009 f150 fwd XLT. I keep having a problem with power to the trailer light recpticals. 7pin/ 4 pin. The first time I had the problen with a blown fuse for the trailer light relay feed. I replaced that one miself. The second time I had the problem, all fueses checked good so I took it to the dealer. Thy repaired the problem saying they rplaced a fuse but they couldn't tell me which one because the mechanic was at lunch. I checked the plug and had power. One year later the first time I went to tow a trailer again here we go again, no power again. I checked all the fueses listed in the owners manual with an ohem meter and the listed fueses check good. Is there a fuse in the system somewhere listed under a different name that can affect the power to this plug.
There is a 30amp fuse and relay in the power dist box marked TT power. This is the fuse that controls the ignition on power to the 7 pin. It has nothing to do with the trailer lights its sole purpose is to charge the trailer battery for RV power or break away switch for trailer brakes.