car wont start, mercury cougar

The other installer at my shop did an i9nstall on an old murcury couger,,and for some reason when the guy electronically rolled down the window his radio shut off, , and the constant wire no longer had current.  All the fuses are fine,  So i fixed that by running a new wire and fuse.   But when we went to move the car it wouldn't start,  it wouldn't even click the starter,,but the battery is fully charged,,we even tryed boosting it, , nothing......everything workes except the starter.  What could it be??   i don't knwo the year,,but it looks late 80's ish

Were you able to test the starter wire for current ? I had this happen to a Prelude last year where I installed a Compustar unit in the car and when I was done with the car, I tried to start it and it wouldn't start. I traced the wire back to the starter output and the wire was not outputting any current. I ran a new 8 guage wire from the starter solenoid to the starter on the ignition column and the car started up no problems. He hasn't had a problem since. I would test the switch as well as the wire for current and continuity from the solenoid.

turns out the starter is dead,,i hate things that happen like that when people get an install done.   The guy tryed to blame it all on the cd player and amp, like common.