stock infinity amp connection located under back seat
 

while routing a CB radio cable i noticed the previous owner had unplugged the two plugs for the amp and spliced the wires of the two plugs together so the amp could be bypassed. there is an aftermarket radio installed and he obviously bypassed the amp for a reason, but is that typical for our jeeps? i am guessing the amp interferes somehow with aftermarket systems.

The Infinity sound system makes it difficult to get sound out of an aftermarket head unit, that is why the factory amp was bypassed.

Actually, you CAN keep the stock amp with an aftermarket radio... look at your radio harness (the black-and-gray one that plugs into the factory harness) and you should see a solid blue wire (no stripes on that wire)... connect that wire to the amplifier turn-on wire on the harness that came with the aftermarket radio (you'll probably have to pull up a manual for your aftermarket radio) and that will send the signal to turn on the factory amp when you power up the aftermarket radio. Many people just wire up the harness, don't see where the blue wire goes to, cut the bare end off, and then turn on their aftermarket radio to see it's not working and no sound is coming out of it.

Since the front door speakers on the Infinity system are coaxial (with a woofer and a tweeter integrated into one speaker instead of a "whizzer" paper cone with a cloth covering over it), you DON'T need to bypass the factory amp if you install new speakers. The real problem comes with the WJ's from '99-'04 with the Infinity system (and WK's from '05-'10 with the Boston system, and '11+ WK2's with the Alpine or Haman/Kardon systems) , where the front door speakers are actually woofers and only reproduce bass due to the stock amp only sending low frequencies to them, and you have to bypass the stock amp front speaker wiring connections by just running the wiring directly from the front door and dashboard speakers up to the radio, or else you'll just get bass, even if you install coaxial speakers in the woofers' place.

i think i get it now, the PO installed some aftermarket speakers and the head unit is an alpine unit so i dont know if it has a wire to turn on the amp or not. it would be nice to use the stock unit to get some more power out of it. i am not familiar with how the wires run, but i assume the wires that were cut over at the stock amp location are the speaker wires?

Almost all aftermarket radios have the blue amp turn on wire.

My first jeep was a 97 POS ZJ that had been ridden hard and put away wet too many times. Under the back seat, the Infinity Gold amp looked like it had caught fire and there was a rats nest of pigtailed and taped wires. I looked at it and thought "Just leave it alone. The radio works." On closer inspection, right next to it was a small oval plate that had been glued to the floor, like an inspection cover. That had come loose and water had gotten to the amp. Be sure you don't have a loose plate.

Yeah, wasn't sure if the color of the amp turn-on wire varied from radio manufacturer to radio manufacturer, but I do know the Scosche and Metra factory-to-aftermarket harnesses use a blue amp turn-on wire. My old '94 ZJ was equipped with the four-speaker system (it was oddly-equipped, with the factory power leather seats (verified by obtaining a build sheet off of Jeep's website), but the A/M-F/M radio with tape deck and the four-speaker system, and the base 28E Package), and my current '02 WJ has the standard (non-Infinity) six-speaker system, so in both cases, I didn't strip the blue amp turn-on wire when stripping all of the other wires to install the aftermarket radios in both Jeeps. There's a few other wires (such as the IP/Instrument Panel dimmer wire) that is also left disconnected in any case due to the setup of the GC's wiring.

Welcome to the forum.

Great that the information was useful.

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Yes, old thread. And I have a question for those who might be following still.

Just bought a 97 ZJ w/infinity gold, CD, Cass, 3-Band Eq, steering controls.

I'm going to buy a new unit with all the modern stuff, Android, Pandora, USB, plus Amp + Sub, hopefully one of those steering control adapters too.

What are the opinions on using the OEM amp?
What about bypassing for better/modern sound processing/tech/power, etc?
Not interested in running wires to each speaker so I'll splice the AMP connection.

Hi😁 I'm installing a aftermarket double din plus external amp & subwoofers. I have an 04 Grand Cherokee Overland with Infinity system. I bought the Metra (factory to aftermarket) wire harness. I reeeally love how awesome the door speakers sound on this factory amp, so I want to keep that part..ok so are you saying that I CAN keep my factory Infinity amp to push factory infinity door speakers when I install this new aftermarket head unit?? All I gotta do is connect head unit's solid blue amp turn-on wire to the factory harness' grey/black wire?? Will that allow me to keep factory amp on doors speakers & have external amp on subs thru my new double din? Or do I need to splice into wires at factory amp too or what??

short answer, yes.

the factory amp is not complex at all..
your speaker wires that attached to your head unit run to the amp along with a constant hot
a switched hot and a ground wire.. the switched hot is the signal or activation wire. I use to have a schematic but I can’t find it. I can look tomorrow ( I’m taking my factory amp out and putting in a nicer amp.)

then from the amp the wiring runs to the 6 speakers