I've got an odd issue with my 2012 F150 I can't figure out. When it gets hot it won't start. Dash lights turn on, power windows work, but no crank. I tested the battery and it's fine. The truck starts great every morning when I start it cold the first time. Also, in the winter, when the truck heats up, both the heater/air conditioner and radio stop working. But these days, the heater/air conditioner and radio don't work at all. Fuses look okay. Problem with a relay? Any ideas?

 

I would start by removing each B+ and ground connections from battery to starter and engine block to give a good cleaning. Resistance increases with temperature and a bordorline connection likely will act up when temperatures rise.