I have a 99 F150 with a 4-way trailer connector. I can get all lights except my left turn. I'm not getting any voltage to that connector (yellow wire). I don't know where to check voltage where the harness connects (near the back tire). The truck signal works fine, so it's just the one for the trailer that's giving me problems. Is there something obvious I'm missing? Any idea what the part number for that harness is? Thanks for any help!!

 

Check fuse F20 under the hood.

 

I think you solved it! I don't have a new fuse here to check it tonight, but the old one is blown. Thanks a million!