What fuse should I use to run my power cable to the amp?
I had a similar problem a few years ago and simply couldn't make sense of it. I traced the power wire back testing it every couple feet and eventually got to the AGU fuse holder. I had ~14v on the battery side and very little voltage on the amp side. It LOOKED fine, and the fuse was fine, but something weird going on in the fuse holder itself simply wasn't making a good connection. I replaced it and was back up and running. I'm not going to say that's definitely your problem, but it's worth a check,
Measure the current (A) drawn in operation, increase by 50% and round up to the nearest standard ampacity: If the drawn current in normal operating conditions is 10A @ 12Vdc, 10*1.5 = 15A, which is one of the standard fuse ampacities (no need to round up).
