Problems with factory stereo reinstall 1993 G20

[jcmurp]

Posted in wrong forum before soHiJust purchased this car at a really good price.They had removed the original factory and replaced it at some point.Before I got the car they had removed there amp and head unit.I was reinstalling the factory stereo purchased from a shop for a 1/93 and newer model(mine is 11/93 model) it has the amps in the trunk on the deck.They had left all factory wiring untouched soooo just plug the factory head back and go I thought.That did not work.This stereo has a pigtail hanging off (a round plug with like 6 holes in it) I can not find anything yet that it plugs into does anyone know? Is it for the amp? anyway I plug it in and try it with the unit out(not mounted) just plugged in and the antenna goes up,lights on and no sound.Anyone help with this? I would greatly appreciate it.I checked the fuses for the amp and they are fine. and how would I check the amps

[the converted]

Try screwing it down and see if anything changes. Nissan doesn't put ground wires in the harness.

[jcmurp]

Well I did screw the radio in the hole and no change.Let me know of anything else you can think ofThanks

[jcmurp]

Fixed it,The aftermarket they had put in blew both amps.Replaced and now all is well(until I upgrade it)