[chitowndad]

I feel sheepish - that did the job! I connected the cooling fan hot wire to the amp switch wire and the fan negative to the amp ground terminal and it works! That was the only thing I didn't try... Thanks!

I didn't realize that the switch wire is a full 12 V when on!

Now my pop sound is back! When I turn off the car it pops. When my amp switch wire is disconnected - which disconnects the amp - there is no pop sound so clearly its coming from the switch wire that I'm running from the head unit harness to the amp switch input...

Any insight is appreciated!

-Steve (a novice stereo guy)