I have a cheap 800 watt amp in the work truck that keeps blowing fuses at the battery, when i hook up the tester to the fuse box it shows that the power wire is grounded on one side and the other side is hot. I put in a new 4ga power wire, took all the screws out of the amp that were touching the metal of truck, all the wires coming into the amp are nice and neat, not overlapping or touching each other. I'm out of ideas on where to look to fix this problem. The amp runs for about 20 mins then the 20amp fuse blows up by the battery. Any Ideas?