Not too sure without opening up the plate of the amp to look at the board. That guy trying to scam you by the way with way. I know that some people have and still do place their amps mounted to theyre sub box in which shakes and rattles the internals of the amplifier loose.You can check the board out, but if you are still under warranty,do not remove the plates/plate.!! Send it back in its original box. If the amp got too hot and shut down on you generally 3 times ,you have to get it repaired.If you put a line inverter in /high level input to low/rca to the rca to the amp supply, that may have become damaged too?? Something to check out,and they are cheap to buy,They dont last 4ever.You can even try another amp just to see if you are getting anything also before you get under the dash to replace that if needed.Any amp should work but use one sub at stereo mode?? or watch the omhs load of the amp n speakers?? Might be the problem??