Amp heating up when powered on

Im having a problem with a Skar Audio amp thats been in my truck and powering a 10" sub for about 6 months now. I noticed yesterday that the subwoofer stopped (while barely playing at a very low level). When I got home, I touched the amp and it was very hot to the touch (about 130 degrees F).

Checked wiring with a multimeter for shorts, nothing found. Checked amp ground for resistance: 2.1 ohms. Amp is getting a solid 13v from the battery using a fused connection. No heat from the wires. Yet whenever powered on, with or without music playing, the amp begins to heat up slowly until it goes into thermal shut-down then cools and turns itself back on and builds up heat until it thermals again.

Ive written Skar audio, but it's the weekend and no reply yet. Anybody have any ideas, or what else I can check with the multimeter?

 

Disconnect the RCAs and the subwoofer. Turn amp on again and see if it shuts down. If it does, the amp is probably going to need to be repaired.

What Skar Audio amp are you running?

 

It does. Tested it outside the truck on a 12v power supply and it heated up again. It's the SK-M5001D Monoblock.