Heart beat sound through my subs

I’d check all your grounds first. The protection mode and the heartbeat sound can be caused by a poor ground connection or a bad ground-loop problem. Even if the amp’s ground connection looks okay, try a different grounding point for the amp and see if that helps. Once the amp’s ground and power connections all check out, then double-check the grounding for all the other car audio electronics in the car including the head unit. You can also try a ground-loop isolator inline with the signal cables, but that will only help if the amp is working and you still get noise (along with regular audio) through the speakers.