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Unread 11-20-2012   #1 (permalink)
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Default 1966 Mustang replacement underdash wiring harness

I bought a replacement underdash wiring harness from CJPonyparts a few months ago, and I finally decided to install it. It is a WUD2. There are some wires and plugs in the harness that dont match up with anything in my manual.

The two most confusing ones is a blue with black stripe with a molded stay-con (which means it goes under a nut with a bolt going through it) and there is a large molded 4 pin socket that fits around the heater area but goes to nothing?? Any ideas as to what they go to??

The blue black (since it's a stay-con) I am assuming its for either the starter or a ground??? If anyone else has installed this harness before your assistance would be greatly appreciated Thank You!!

Last edited by rcatransmitter; 11-20-2012 at 08:02 PM. Reason: grammar
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Unread 11-20-2012   #2 (permalink)
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I've never purchased a wiring harness yet but if I had to guess by what you wrote, I'd say the 4 plug connector either goes to the heater resistor or the hazard switch in the glove box. The other wire possibly goes to the back of the ignition switch or a ground on the dash panel. without seeing the connector or wire I'm guessing here to try and offer some ideas. let me know if this helps. joe
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Unread 11-20-2012   #3 (permalink)
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I replaced my 66 harness with the same one. Without looking at it I think that blue-black wire is for the courtesy lights. One wire is for the light and the other for the ground, which can be screwed to any metal near by. The 4 plug you mentioned I think is for the heater resister.

Also to let you know, that harness will have every lead to all options that could have been installed on your car. Meaning, you will have leads from that harness which will not go to anything because you may not have that option. Hope this helps.
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Unread 11-21-2012   #4 (permalink)
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Get a 66 wiring diagram from any of several sources. It will allow you to answer your own questions without too much heartburn. I am assuming here that the harness you purchased is one of the direct replacement harnesses, not one of the alternative wiring setups like Painless Wiring or other companies provide primarily for street rods.
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Unread 11-21-2012   #5 (permalink)
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I have all of the drawings and manuals available for this car, but no blue black wire :-( with a stay-con
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Unread 11-21-2012   #6 (permalink)
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It is indeed a factory replacement harness not the Painless one.
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Unread 11-22-2012   #7 (permalink)
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Hello Scott.

First of all, welcome to AFM. Second, I always love a mystery. Even better if I finally figure out what seems to be an answer. Third, if I had shelled out that many $$$ for a harness I would have wanted it to be correct with its colors just like you seem to expect.

Let me ask who made the harness that you bought? Alloy Metal Products? I have no experience with any other company and I would have thought they would do a better job with wire colors.

I agree pretty much with Joe's original reply except that the 4-pin socket would not go to the heater resistors since that is only a 3-pin connector. I am thinking it is for the Emergency Flasher Switch in the '66 glovebox but a picture of what you have would help determine that. No part of the underdash harness goes through the firewall so nothing on it will connect directly to the starter.

Sta-con is a term I am not familiar with and a Google of the name seems to indicate it is a company and not any particular style of connector. I think what you actually mean is a 'ring' connector which has a closed ring of metal that fits around a bolt or screw. I also think that ring goes around the stud sticking out of the back of your ignition switch. The ring connector is shown on the '66 Exterior Lighting, Turn Signals and Horn schematic. I suppose you know about the schematics site: Mustang Wiring and Vacuum Diagrams There is a link to it at the top of the Classic Tech page.

To come to that assumption I looked at the picture of your harness at CJ and it shows a ring connector just about where I would expect it for the ignition switch. AND the '66 schematic shows a ring on that stud that is supposed to be black-green. How yours got to be blue-black I don't know. All the way back to 64.5 the schematics show that as black-green. Prior to '66 it was wired a little differently but the ring was always on the ignition switch stud.

Too bad an ignition switch is so hard to see once installed or I would take a picture of my '66. Instead I have a picture of a junk harness I scrounged from a breakers yard 30 years ago. It is a '65 of some sort (maybe even a 64.5?) and shows the ring connector on the back of what's left of the ignition switch. Notice there are TWO wires molded into that ring connector the biggest of which is black-green. The second, smaller one is just plain black. NONE of the schematics I find show such a double wire that includes plain black!!

Check that your blue-black goes to where it should on the schematics. If I am correct, for '66 it will go to the orange-yellow wire on the turn signal flasher, a green-red wire on the voltage regulator, the fuse block and a black-green to the instrument CVR. Those 4 connections are shown on FOUR different Mustang schematics which is not uncommon for the way they drew these.
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Unread 11-29-2012   #8 (permalink)
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The harness is a Mr. Mustang 14401 66. I have tried calling them over and over and no one there bothers to answer their phone?? I don't know how CJpony or anyone else can answer from them when they wont answer?
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Unread 11-29-2012   #9 (permalink)
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Ill agree its for courtesy lights. I'm having major issues with my wiring but today I solved 99.14% of the problem. That be said, I've been messing with that black and blue wire which is the courtesy lights. There's a green and yellow I believe is the mix which is the courtesy light too.
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Unread 11-30-2012   #10 (permalink)
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My wire that I am having an issue with is a blue black and is supposed to be bolted to something??
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Unread 11-30-2012   #11 (permalink)
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Sorry to hear you purchased a Mr. Mustang harness. Its the low end of harnesses when compared to alloy metal products. Mr Mustang is approx. 15 minutes from yet they are not often open or available so I dont fool with them.

As for your Ring tongue terminal. Its a ground wire. You wont find a ring tongue terminal or an underdash harness that supplies power t anything.
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Unread 11-30-2012   #12 (permalink)
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well there are 2 "ring tongue" wires that go to the ignition switch so I didnt want to not connect it up to the wrong place
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Unread 12-01-2012   #13 (permalink)
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Sorry to hear about the Mr. Mustang harnesses quality. I had never heard of that name and all mine have been Alloy Metal Products which aren't without some of their own problems but I have never had a wire color swap on theirs.

Rick,

Take a look at the picture I posted above. It shows a ring connector on the back of the ignition switch that is definitely NOT a ground. That is the #297 wire on the schematics (which is even drawn as a ring) and it goes to the places I listed above. Exactly where the 2nd black wire on that ring goes I don't know but, as I said, that photo is from an old '65 harness.

Scott,

You say there are two ring connectors that go to the ignition switch in your harness. There is no ground in an ignition switch. The schematics show a second ring on that power terminal provided you have A/C. The second ring is a #358 (yellow) and supplies power to the fuse for the A/C blower under the dash. That might be what they have given you although it would not have been on an original harness.

If the company won't answer your calls you will have to figure this one out yourself. Somewhat ignoring the colors you need to trace the wires to see where they go and compare them to the schematics from the link I posted above. I am nearly certain that the ring(s) you see are not grounds. The ring ground connectors are all on the other side of the items that get power from the main harness. Since none of those items are included with a harness their ring grounds will obviously not be on the harness. The only ground ring I see on a harness is one on the alternator harness which is obviously under the hood. And remember that there are FOUR (at least) sheets of schematics and each one can show a different connection to the same terminal. You have to combine all possible connections from all 4 sheets to know what you should actually have for a harness.

The two power supplying rings are in the upper left corner of the attached snippet from the '66 schematic.
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