Have an older good custom system (Pioneer receiver, good speakers, couple of Amps - mounted in the trunk). It works great with one caveat. Whenever it gets hot outside, one of the channels goes out (sound only comes from one side). It seemed to me that it is caused by heat buildup. I checked wiring and connections and all looked fine. I'm stumped...any ideas? Thanks, in advance, for your suggestions.

My gut instinct would be the receiver. You could try isolating each amp, individually, just to be sure.
Loren
SW WA