Recently got a free amp and subs from a mate of mine because the amp was driving him nuts. He couldn't work out why it would works sometimes and not others. After a fair bit of testing I've worked out how to avoid the problem but not a nice solution of the cause of the problem. Pretty much the amp will go into protect mode if ACC is turned on or the car is started (so pretty much when turning on the amp) while the RCA's are plugged in to the amp and into a HU or iPod at the other end (so if the circuit is completed). So it'll work if i unplug the RCA's from my ipod then turn the car on then plug them in. I have opened the amp up and nothing seems blown or broken in any way. Any thoughts?

line input might be set to high?