Spooky stereo on ZJ - insight needed
 

I have a 1995 Jeep Grand Cherokee Limited with 177,000 miles. I recently started fixing some of the many things that are no longer working. One bright spot was the Infinity Gold sound system - very cool. I had recently put new foam surrounds on the door speakers. Played great. Then it didn't. Radio came on, clock worked, searched stations - no sound. Checked the amp under the rear seat. Ground was good. Fused violet wires both had 12v. Even with ignition on and radio on the gray/orange wire to start the amp did not have voltage. Just as a check I jumped a violet 12v wire to the gry/org wire - SOUND. Great, the amp came back to life. I disconnected the jumper. Radio still played. I turned it off and back on - still OK. Turned the car off and back on, I still have a sound. What the heck in going on. I don't think it is possible to jump start an audio amplifier, but that seems to be what I've done. Any insight would be appreciated.

Possible the radio experienced a short to ground when sending out the speaker signal and cut audio output temporarily. Had that happen on and aftermarket unit on my XJ. When I rechecked wires and ensured they were not shorting I restarted the radio and it worked fine.