sound problems, 4ch amp

I just replaced my 4ch amp that crapped out on me a few months ago, I've been just running my rear speakers off my sub amp for the time being. Everything had worked fine before the amp stopped working, but I hooked up the new clarion quickly the other day and it appears only the rear rca outputs from my head unit are supplying sound to the amp. so in 4 ch mode i only get sound to the rear speakers. Its not the wires I swapped both, and in 2ch stereo mode I get "fake sound" to the fronts. And is this wasn't bad enough the amp cuts out on me occasionally real quickly and starts working fine when I turn it down. I suppose this is an electrical problem. But if anyone has any ideas on these problems I'de appreciate it, thanks
 
Hey im not too sure about your front speaker problem in 4ch mode...but for the amp cuttin out.....where do you have it placed? i had my old amp in my old car placed in too tight of a spot and it would over heat and cut in and out....dont know if thats your case but it might be...good luck