check the accessory fuse. 99% sure that's your problem.

in fact, don't just check it. replace it.

 

For an aftermarket HU, you should have tapped into a switched power source (usually ignition). Check that tap and make sure it is still intact. If it was installed by a shop (Best Buy did this on one of my older decks), check for an in-line fuse on this line.

And as Phil pointed out on another thread....fuses do not have to LOOK bad to be bad.

John

 

Thanks all for the advice, I'll be trying those out tonight.

 

It was the Accessory fuse - it looked OK at a glance but a careful inspection showed the break. I was starting to go crazy driving around Houston without any music.

Thanks PJK3 and all others!