So my step-brother has, like a 94 Jeep Grand Cherokee, and wanted to swap head units. No problem. The old one worked fine and dandy. Went to Best Buy and bought a new head unit. He wired it up and all seems to work, but nothing is coming out of the speakers. He put in the old radio and they worked again. Hmmmm..... Next he used a multimeter to make sure the new headunit was even putting any current through the speaker output wires and there was. So now he is stuck...Any suggestions? TIA
-Steve

 

If it's a 94 Jeep Zj then it's 99% of the time got an infinity amp wired into the speaker leads. You'll find it under the rear seat on the driver's side but you won't need to touch it.

Simple fix: Pull out the cd player...Take the power antenna wire from the car's harness and hook it up to either the deck's remote wire or just tie it into the ignition wire for the harness. This should fix the problem.

HTH!