Not sure what happened there with your unit, but it might have been one of the two that I sent back due to not having enough clearance for the heat sinks. I burnt one out fairly quickly, got a replacement, then a couple of weeks later the replacement went bad also. It did not say in the instructions, but I figured out that there needed an air gap on the back so I added 2 flat washers to each hole. This offset the unit just enough to flow the air through. Have hundreds of hours on the third unit now with no problems. They never gave me one minutes' problem about the exchanges. I then had one of the speakers start rattling so I contacted them again. They then sent me not one, but two speakers. I can't say enough good things about the way Shark has treated me. Hope they get you straightened out.
Also, I ran a separate dedicated circuit directly from the battery with an in line fuse and a shutoff switch. Now, when I turn it off, it is completely off. No battery drain that way. And, the amp is so hot, it is excellent for putting fast food in the frunk to keep warm for on the way home.