radio wiring help

[888pineapple888]

Hey I'm looking to install an aftermarket radio, but the wiring has me confused. The radio (am/FM/CD/tape) in my 03' has three connections on the back one long and flat, one a smaller rectangle, and one a square. The last two mentioned can be unplugged with sound still coming out and the radio still responding haven't had a chance to see if the buttons still dim with them disconnected. Does anyone know what the connectors are for? Its easy to find a harness for the long connector, more difficult to find the others. Do I just leave those two connected to nothing?! I do have a picture of the back of the radio to show the ports but cant get it onto here on my phone if i cant figure it out ill post it from the pc. Any info is appreciated, thanks.

[888pineapple888]

here is the back of the radio (posting from tapatalk isn't showing the thread as mine in the app but I'll roll with it)

[IPreferDIY]

I don't know the details, so I'll just provide some general comments until someone else chimes in.

I'm pretty sure one of the connectors would be for a CD changer. The wiring for one would normally be there even if the car didn't come with one. If you do have a Ford CD changer, I have a hard time imagining there would be a way to get that to interface with an aftermarket unit, though I could be wrong.

The other one I'm not sure about. Something I've heard about is some cars having the capability to adjust volume based on speed to compensate for road noise, so it might have something to do with that. I had a quick look at the following owner's manual (I presumed MGM) but didn't see anything about such a thing:
http://www.fordservicecontent.com/Fo.../03grnog4e.pdf

The main connector should have all the power and speaker wires you need, and the harness instructions for that one should tell you what's what. I've never had any problems not worrying about the other ones on my 2000 MGM.

[888pineapple888]

Yah it is a mgm, I don't have a CD changer so that won't be a problem (I ditched CDs a while ago anyway) the speed adjusting vol is an interesting thought but I don't think my car has it, pretty quiet cabin anyway. What I don't get is why connectors would be there AND plugged into the unit if they went nowhere... Though, if you have the two of those hooked up to nothing in a 2000 I doubt I'd have a problem, these cars changed very little over the years...

[888pineapple888]

Looking at the harness on amazon I believe the square is for a factory subwoofer. The description mentions a "factory subwoofer retention harness" where the connector leads to blue wires (assuming they're remote wires) and rca jacks for audio. The other must be for a CD changer... I don't know if these cars had these as factory options but the radio was most likely used on several models...

[888pineapple888]

The model number on the radio is 3W7T-18C868-AF if that helps

[IPreferDIY]

Here's something interesting that I found (though I can't vouch for it):

http://www.justanswer.com/mercury/5k...g-diagram.html

http://ww2.justanswer.com/uploads/ap...nd_marquis.pdf

I don't bother with factory stuff myself. I don't even use the factory connector anymore (except maybe for a power line if I need one), since I use 12 gauge speaker wire and direct lines to the battery (fused, of course).

[888pineapple888]

It gives credibility to the subwoofer hookup being for part #18c804 (factory sub) and a CD changer for part #18d806 (factory 6disk for trunk) not that it's a positive match to the connectors, but it's good enough for me to not worry about it. Thanks a lot

[tjc78]

Everything you need is in the large plug, just tuck the other two away.

[sly]

Pinouts and other info: http://www.cvpi.org/archives/p71inte.../wsdindex.html

[888pineapple888]

Thank you, that clears it up 100%