I'm try to figure this out. First of all I have 4 6x9s in a liquid trends box on my tower. Heres my problem, it seems that I may have a short or something because when the two on the left are working the two on the right are not and it switches out sometimes from the right working and the left not. Rarely they all 4 will be working at the same time. Its seems that if I turn my head unit off for a couple of minutes and turn it back on they all work fine. I have checked all the wiring and can't seem to find the problem. I'm starting to think it may be the head unit but, I'm not sure because the rest of the speakers work fine. Maybe you guys know something else I should be checking. thanks

2/4 channel amp? more info. what HU. sounds like a channel issue, but no idea really.

Sounds like a bad ground or a loose connection to me

Could be short or loose connection but if so, turning the head unit off to "cool down" shouldn't effect a short etc... I assume your running an amp, if so it's likely in there instead of head unit.