Need Help with wiring an 87 GT Convertible Radio

DannyB1122

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Sep 17, 2012
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Hi Everyone,

So I'm relatively new to the forums, and I am definitely new to owning a Fox Body. A couple of weeks ago, I bought a pretty sweet 87 GT Convertible (much to my wife's chagrin, of course lol). The guy I bought it from is a mechanic, and took great care of the car. There isn't a spec of rust anywhere on it, which after 33 years, is quite the feat. The only downside is that when I bought it, he told me that the radio didn't work. Now, I've installed aftermarket radios before, so I didn't think it would be a huge deal. Was I wrong...

The owner before the guy I bought from (I believe this was the original owner) installed an Alpine receiver in the car. Because it was broken, I pulled it out and then bought a new head unit and a wiring kit. As I took the radio housing out of the dash, I found a venerable rat's nest of wires in there that took me several hours to trace back. (Aside from the fact that it was wired as if someone were reading a "dummies" book while they were doing it, but I digress.) Turns out that whomever installed the Alpine receiver in the car cut into the factory wiring harness. And of course, there are three wiring harnesses in the housing: one with a wide gray plug for power, one with a wide black plug, and one fat gray one. Long story short, I wired up the adapter between the new radio and the factory wiring, and while the new radio gets power, no sound comes out of the speakers.

I flipped through the paperwork on the car and found that it was originally built with the premium sound system, so it has 6 speakers. I have a wire-tone generator, so I confirmed that what I thought were speaker wires were actually speaker wires (connected to the fat gray plug noted above), and also confirmed that all 6 speakers are operable. But, I can't get sound out of the radio for love or money. Does anyone have any ideas?

Much appreciated.
 
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DannyB1122

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Sep 17, 2012
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Factory amp was removed and I saw another wiring plug all the way in the back, closer to the firewall and up a bit. Same type of plugs (wide black and gray). Could that be it?
 

DannyB1122

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Sep 17, 2012
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For whatever reason, I have a set of gray and black plugs in the front (closer to the shifter) and one in the back (closer to the firewall) in addition to a set of two gray fat plugs in the middle. I took pictures for reference. Whomever hacked this thing up did a spectacular job!
 

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Mustang5L5

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I can’t tell from the pic, but verify that when the factory amp was removed, the amp harness was also removed

Looks like this.

4896C309-ED42-4C44-9CB3-7815700688A0.jpeg


With the amp removed, if you attempt to connect to this harnes you will get nothing.

You need to unplug it, and connect to the two plugs that go out to the speakers and power connections
 

Mustang5L5

i'm familiar with penetration
Mod Dude
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In fact, looks like it is in place. You need to pull that out and disconnect the rear connections. Remove the harness, and then connect your radio wire harness to those plugs
 
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90sickfox

I didn't really have an issue with the stink...
SN Certified Technician
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Looks like your amp is still in there. Also looks like they ran aftermarket speaker wires... two purple, two gray, two green, two white. You could try tapping into those wires to see if the speakers come on. Those wires at the back need to be followed. The amp is usually mounted to the trans tunnel back there...but looks like yours may be tucked up above. Hard to tell without digging back there myself.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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Actually, now that I can see the pic on the PC, that is exactly what is happening. Your AMP is missing, but the wiring is in place and you are trying to wire the radio into the amp harness which won't work.

See this connector? there should be a matching grey one as well. Unplug these, pull the amp harness, and plug the radio into those plugs.

1585834537559.png
 
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DannyB1122

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Sep 17, 2012
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Awesome. Thanks guys. I’ll try that later this afternoon after work. Between this quarantine stuff and this radio, I’m about ready to start day drinking lol.
 

DannyB1122

Member
Sep 17, 2012
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Thanks guys. I was able to pull out the amp wiring harness. Found something interesting though. The door speakers were wired into what I'm assuming was the old amp output wire connector (one of the fat gray ones), I think in an attempt to make a three-way crossover into the old Alpine unit that the previous owner installed. My new wiring harness from Crutchfield is coming tomorrow, so hopefully by this time tomorrow night, I'll be listening to music with the top down...
 

Mustang5L5

i'm familiar with penetration
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WIring diagrams are here if needed

 

DannyB1122

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Sep 17, 2012
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Ok, so as I was in the process of removing the amp wiring harness, I found that the door speakers were still wired into the amp plug. So now I have three plugs inside the hole: one gray one for power, one black one for speakers, and another fatter gray one that has 4 wires coming out of it, 2 for each door. I put a trace toner on all of the wires and confirmed that all 6 speakers are intact and operable, as I get tone from each when I connect to its wire under the dash. So far, so good, right? As soon as I plug in the head unit, I get no sound at all. When it powers on, I get a very light "pop" sound coming from the back, but only when the head unit powers on, never when I connect to the trace toner. (Same sound was made when you'd power on the old Alpine unit that was in the car when I bought it.) Thinking that it was the radio, I exchanged it for the same model (JVC) and even the new one doesn't push any sound. I reconfirmed that all the speaker wires are intact and operable. Short of having to get this thing professionally installed, which I don't really want to do, I literally cannot figure out what the deal is with this.
 

90sickfox

I didn't really have an issue with the stink...
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Sounds like a short to ground in the speaker wiring somewhere. If you ground a speaker wire on most systems it will kill the sound from the radio for protection.
 

90sickfox

I didn't really have an issue with the stink...
SN Certified Technician
Mar 2, 2015
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To be honest it would be easier to run new speaker wire from the radio to all of the speakers. It could be that there is a loose wire in the door panel, quarter panels, or behind the dash speakers that's touching metal. I would start there. If factory wires look good then you could try wiring each speaker one at a time with the radio on. When you get to the shorted one the sound will stop. The wires you have under the dash that are white, white/blk, gray, gray/blk, green, grn/blk, and purple, prpl/blk need to come out if going back to factory wiring. The radio harness should say on the wires what speaker they are supposed to run to in tiny print on the wires. Sounds like you inherited a pretty jacked up wiring issue.
 

DannyB1122

Member
Sep 17, 2012
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Makes sense. I may have inadvertently started down that road yesterday. Completely redid the wiring and then attached the rear speakers, still getting nothing. So of there's a short, I'm guessing that it's probably one of rear speakers...
 

90sickfox

I didn't really have an issue with the stink...
SN Certified Technician
Mar 2, 2015
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4,268
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Also, make sure the radio black wire has a good ground. If the ground is weak it can cause similar issue but the screen usually will black out for a split second.
 
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