protection mode may not be overheating, often has to do with current draw. I am not sure if i am understanding the post correctly. RCA to headunit and remote power to the headunit. The amp needs 3 connections for power and a signal from RCAs. Ground-from amp to chasis// Power wire- fused directly from battery to amp// and the remote wire- 12V with very little current from headunit to amp, this wire is usally blue and goes from the headunit to the REM connection on the amp. Each of these has a seperate terminal on the amp.