Pitbullpride

I just realized I probably posted this in the wrong spot so I edited it to say Hello all... newbie here... Ok, so I got robbed today, but maybe not. I bought a kicker cx600.5 amp off craigslist for 75 bucks... I got it home to install it in my sons car and fpund out that the amp currently stays in protect mode, except for a split 10th of a second that it switches to reg mode then right back to protect. I have alot of mechanical and electrical knowledge, however none with amps. I have the basics to test with, but no knowledge with amps. All that said, I assured 1st that a good power supply, and ground was present as well as disconnected the speaker wires (that work fine with anpther smaller amp) as well as disconneted the rca jacks... Still the amp remained in protect. So, here is the start of a new venture, could somebodyhelp me with a step by step diagnostic as well as direction with this, possibly so I could get my sons car up and thumping..