I have a 77 ford f100 I am restoring. I have two factory am/fm radios. I bench test both with antenna male plug all the way in, and the fm works fine on both radios. The only way to get am to work, is to slide the male antenna plug all the way out till it is just touching, then if I jiggle it, the radio plays. Any thought on this?

 

as I posted on the other forum, make sure the center pin on the antenna cable is making contact both internally and in the radio.