SHELBY GT 350 Member
Joined: Sep 2010
Location: see user name
On second thought, before you go trashing the unit be sure to verify that it's getting ACC (switch) power. In case you don't know much about this, car audio head units receive power from 2 wires; one is constant and the other is switched. Given your symptoms it sounds like the constant power supply is good, but the switched (ACC) side is not.
As mentioned previously, start with fuses. Then if that checks out move on to this. You will need to pull the head unit out and probe the wiring harness terminals with a voltmeter or if you don't have one of those then a 12V test light will work just fine.
It's a little bit overkill to go through all of this - if the fuses are good then 99% chance the unit is receiving power as it should, but since we're currently in the business of speculating and diagnosing things over the internet, thousands of miles away from one another then I'd rather give you an overkill recommendation just to be sure before you go out spending money on new stuff only to discover that I was wrong when your new unit doesn't fire up as it should.
2001 GT Convertible
All the usual bolt-on's /200 I6, C4
And a few Explorers too... 2008 4.0 XLT 4x2, 1996 XLT 5.0 4x2, 2003 Sport Trac XLT 4.0 4x4