Car Stereos: head unit install, jeep grand cherokee, infinity gold

Question
My father in law has a mid 90's Jeep grand cherokee limeted with the infinity gold stereo that the factory head unit quit working. I know a little bit about installing stereos so he aske me to help him put a sony after market head unit in> After wiring it up it worked put wouldn't play threw the speakers. If you wire a speaker directly to the head unit it works though. I know it has the infinity amp under the back seat so do I have to wire around that, buy some special wiring box that works with it, or replace it cause it may be blown also?

Answer
Hi Jason,

In a mid-90's Grand Cherokee with an Infinity system, you simply have to activate the factory amplifier when you install a new head unit.  This is very similar to activating an after-market amplifier: there's a wire in the factory radio plug that will turn on the factory amp if you apply voltage to it.  You simply need to locate this wire, and connect it to the blue/white remote output at the back of the Sony deck.

The wire you need is at one end of the black plug in the radio cavity.  The factory wire color is typically dark green with a red stripe.  If you're using an adapter harness, this wire will line up with a blue wire in the adapter.  Just connect it to your Sony deck's blue/white wire, and it should turn on the amplifier when you turn on the head unit.

If you're still not getting sound, I'd check the fuses.  The Infinity amp should have its own fuse in the vehicle fuse box; a blown fuse will result in no audio output.  There's also a possibility that the factory amplifier is defective--its location under the rear seat sometimes makes it vulnerable to moisture.  In this case, you would have to bypass the amplifier.

Provided the factory amp is still working properly, you don't need any special module to integrate it with the new head unit; you just need to turn it on.

Hope this helps!

Brian