Car radio fault

[didikai]

My car radio sometimes just outputs the right channel. But if I turn the volume up, it switches back to stero.
This is the second audio unit in the same vehicle so I know it isn't the radio.
What should I be checking?
Thanks

[gadgetguy]

Sounds to me like a poor connection offering high resistance. Check and reseat your speaker wiring connections. If they're alright and reseating doesn't fix the problem, then it's probably a pinched/worn spot someplace in the wiring harness, most likely where the wire passes through any structural steel or maybe pinched behind any decorative molding.

[Xylob the Destroyer]

Is the slot you have your stereo mounted in deep enough to hold it?
It could be pushed to close to the firewall or something inside the dash and smashing the connections and wires on the back.