1988 Fox Radio Wiring Problem

[plantmeister]

Hello all,

I'm new to the Mustang universe, but I've been off to a running start. I got a mustang that was sitting in storage for over a decade, so this thing is 100% stock.
The being said, I recently purchased an aftermarket radio to put in. When I pulled the original stereo, I didn't want to cut the harness, so I bough the kit you can get on LMR. I wired it up and got power to the radio. Then I wired up one speaker and bam---sound.
I proceeded to wire up the rest, but here starts the problem. When ALL speakers are wired up, everything becomes extreme low volume. I can barely hear it at max volume.
I undid all the wires and hooked up passenger front. It worked perfect. I hooked up the drivers side front, along with passenger side front, and it's back to extreme low volume. It appears that more than one speaker wired up causes this. Also, even if only one set of speakers (+,-) is wired up at a time, it's only the passenger front that works at normal volume.
I looked in and it does still have the premium amplifier, which I'm trying to avoid dealing with. I checked back speakers before I gave up for the day, and discovered one was blown. I wired up, avoiding wiring that speaker, and still have low volume.
For kicks, I hooked up the original radio to the original harness, and I encounter the low volume issue. It can't be the new radio I just bought, or the new harness...so I'm left to car wiring and speakers.
What can be causing this? Where do I need to start with repairs to get this radio in and functional?

 

[General karthief]

Are you wiring it up through the amp or by passing it?

 

[plantmeister]

No bypassing. I hooked up an adapter wiring harness to the ones that are coming out of the amp that was already there

 

[RaggedGT]

The simple fix I believe would be to run new speaker wire to each speaker and use the factory harness to power the head unit. But for an actual wiring diagram/fix for the factory amp
@Mustang5L5 or @jrichker may have some advice/knowledge for you.

 

[General karthief]

Have you tried by passing the amp, I think you are confusing the amp by using an aftermarket radio, harness to amp plugs are the same as amp to radio plugs.
You aren't play'n rap are you? Fox bodys can tolerate country but not rap, mine likes the doobies, 38 special and the like.

 

[Mustang5L5]

You'll need to bypass the amp. Most aftermarket head units are amplified so wiring them in series with the factory amp tends to cause issues.

yoi just need to disconnect the wiring to the amp, remove it if you'd like (to eBay it as they have some value) and run the radio wiring direct to the speakers.

You will lose the door speakers however this way, so you'll either need to rewire the speakers, or run the dash/door in parallel with a bass blocker on the dash speakers.

If you really want to do this correctly, just leave all factory wiring alone and run new wire.

 

[General karthief]

I bypassed my amp in the 89 gt with a plug in adapter and all my speakers worked, factory wiring.

 

[plantmeister]

So in essence, I need to bypass the factory amp.
I've never done anything like this before. Is there a detailed article, or can one of you guide me through this? Thanks!

 

[General karthief]

Sure easy job, the amp is behind the radio with radio removed you will see two bolts that hold the amp to the console brackets you should be able to slide the amp to the passenger side foot well after removing those bolts unplug the wires and plug your adapters into those conectors than bring them out through the space where the radio lives.
You should not have to cut any part of the car harness to install aftermarket radios
SAVE THE ORIGINAL RADIO AND AMP!
If you don't want it pm me
They also make kits to mount most aftermarket radios in the dash so you shouldn't have to cut up the dash too.

 

[plantmeister]

Thanks for the info! We removed the amp, but the wiring that was plugged into the amp doesn't seem to be compatible with my kit I bought. The amp harnesses are double row, and the kit I bought only matches up with the regular harnesses, a single row. Where do I plug up my radio? I might be over thinking this

 

[plantmeister]

Okay, here is the current situation:
Bypassed the amplifier. Hooked up my wiring harnesses to the factory harness, all power was correct, and all speakers are correct. Now there is no sound at all. The amp harnesses are not hooked to anything.
I can't figure out where I've gone wrong. Why can't I get it to work? Everything is hooked up right.

 

[General karthief]

That looks like the same wiring I have and my kit pluged into those wires all I had to do was connect that adapter to the one for the radio.
I will look at my amp and my radio I still got my original stuff.

 

[plantmeister]

Here is one last picture of what I'm looking at (sorry that everything keeps getting turned sideways )
The smaller, square ones were what was plugged into the factory amp. The skinnier ones in front were plugged into the stock radio. I have adapters to fit these, but not what was plugged into the amp.
Now I'm getting no sound at all, even though I still have power to the radio (which seems to be getting somewhat hot if that means anything at all). So, I wonder if I need to do something with those plugs that went to the amplifier. Do I need an adapter for those or something of the sort?

 

[General karthief]

I just pulled all my old stereo stuff I took out. Mine has an graphic equalizer filter under the passenger seat. The plugs that go into the back of my original radio are two long black plugs.
You you have two long black plugs?

 

[General karthief]

I can pull my aftermarket radio out in the morning and see where the wires you need are coming from. My car had the premium system with the graphic equalizer and filter, my book only shows that system, they all came this way?

 

[plantmeister]

Morning!

The two plugs I pulled out of the back of my stock stereo are rectangular black, and one is grey with black.
The other two that were plugged into the amp are square and gray.
Mine has 6 speakers, with the amp. I haven't looked under the passenger seat for anything.
Hopefully that info helps. The picture I posted has every connection available in it. I hope there is just one last step to get sound coming out of my stereo

 

[jrichker]

Maybe this will help...

For more help and parts for what you need to do, see http://www.crutchfield.com/Support/Support.aspx They have adapter harnesses and harness kits to fit all kinds of cars and radios.

I highly recommend them, in the past their support has been very good.

 

[General karthief]

I inspected my stereo wires and I have two flat black plugs coming from a harness that runs along the lower rail of the dash near the rt corner of the console. They onlt extend 4 or 5 inches from the harness. My adapters plug into those black plugs, one plug has red, green/lt green stripe, orange, blue and a couple others the other black plug has bright colored wires, pink, yellow, green and the like
Hope this helps

 

[Mustang5L5]

There's a secondary harness inside that you need to remove as well

This is the amp harness, and as you can guess, the two top left plugs are what plugs into the amp.

Then you can see the two sets of plugs that look like they will both connect to the radio. Ford basically plugs the amp in series with the body harness. Reach DEEP up under the dash and look for the second set and disconnect them, and then pull this entire harness out.

Now, the two ends you are left with should plug into your radio harness.

And as mentioned before, do not toss this stuff out. It's rising in value and there is a market.

 

[plantmeister]

Oh, so, I need to disconnect the middle two and it should work just fine through the two radio connection harnesses? This is way more complicated than I thought.
Is there a trick to getting these unplugged? I've looked back in the dash and I'm afraid to unplug anything if I don't know what it connects to; it's very difficult to see back there.
I went onto the Crutchfield website as suggested and ordered an amp bypass harness. I hope that works, considering how much I've paid for all of these connections and kits so far.
I've kept the amp set to the side for now, and I'm avoiding cutting wires for the fact of market value on stock items.