Testing an Amplifier/HU

[Tommy]

How can i test my ampifier to see if it is recieving signal from the HU?

my amp powers up fine, and runs most of the time, but it dies sometimes, green light on everything, but no sound from the speakers.

I think the sub-out on the HU might be the culprit, is there a way to test it?

[Hatch]

you can hookup a voltmeter to the sub preouts.

[ZXLNT]

Swap the pre-outs from the HU to the amp and see if the problem follows the pre-outs or follows the amplifer. If it works with another set of pre-outs then I would look at the amplifer. If it doesn't work then look at the HU for the problem..