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Parts Wanted Alternator Wiring harness

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Joined
Feb 8, 2014
Messages
312
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101
Location
Austin, Texas
My Car
1971 SCJ Green
1971 CJ Pewter
1973 H-Code Copper
1967 Q-Code Galaxie
I am looking for the alternator to voltage regulator wiring harness for my 73, a/c car with gauges. Please me let me know if one has one.
 
Just checked, the version I have is for the 70 AMP alt. 70 amp alts are used on Mach 1s with rear defrost.
Thanks for checking, the harness I need for 55 AMP or 65 AMP. My 73 car has very few options. And just confirmed it is not even a 73 alternator (auto zone) special, so I guess I need to find the correct alternator also.
 
I have the harness and an alternator. Not sure if this is what you need. Came off my 71. alternator.jpgalternator 2.jpg
 
NPD has the non-gauge harness in stock

https://www.npdlink.com/product/wire-loom-alternator-feed/175763?backurl=search /products?search_terms=alternator%2Bharness&top_parent=200001&year=1973&year=1973

The guage package harness is out of stock

https://www.npdlink.com/product/wire-loom-alternator-feed/146050?backurl=search/products?search_terms=alternator%2Bharness&top_parent=200001&year=1973&year=1973

The actual year of the alternator won't matter unless you're going conours. The 1G alternator was used through the 1980s. Most I've seen are spec'd out to be built to the 60 amp standard.
Hemi killer would you know what the wire in the bottom slot of the connector is for?
And why the harness listed for center gauge equipped cars doesn’t have a wire in that last slot?
I bought the one from NPD for a 72 with gauges and there is no wire in that position and my alt gauge doesn’t work.
Thanks
 
Cars with ammeters have only 3 pins used on the voltage regulator plug; alternator indicator lamps require a 4th pin. Furthermore, there is a difference in wire placement between the two.
 
You'll need the alternator harness with 4 pins used. If so, you could have a bad bulb, a broken wire somewhere, a bad ignition switch (proof-out circuit), a broken trace on the circuit card, bad contact at the voltage regulator, a bad voltage regulator, or bad contact at the dash cluster connector.
 
You'll need the alternator harness with 4 pins used. If so, you could have a bad bulb, a broken wire somewhere, a bad ignition switch (proof-out circuit), a broken trace on the circuit card, bad contact at the voltage regulator, a bad voltage regulator, or bad contact at the dash cluster connector.
I have a center gauge ammeter car so I need the three pin harness which I have correct?
Are there any good wiring diagrams that show this set up?
Thanks
 
Hemi killer would you know what the wire in the bottom slot of the connector is for?
And why the harness listed for center gauge equipped cars doesn’t have a wire in that last slot?
I bought the one from NPD for a 72 with gauges and there is no wire in that position and my alt gauge doesn’t work.
Thanks


The difference is in how the regulator is controlled. A non-gauge car uses the warning light circuit (Green w/red stripe #904) through the I terminal to energize the alternator field coil, and the stator output (White w/Black stripe) through the S terminal then closes the field relay in the regulator. A gauge car has that circuit, minus the warning light, but it is wired through the S terminal to the field relay inside the regulator, and battery voltage (Yellow w/white dots #36) through the A terminal then energizes the alternator field coil.

1709135986476.png

If you want to get into the weeds, download the PDF attachment below. Some of the circuit numbers may not match as the author has a '69.

If the ammeter doesn't move at all, I've sometimes found them to be wired incorrectly. Both the Black w/Orange stripe from the alternator (#38A) and the Black w/Orange stripe from the main harness (#38) must be on the terminal block mounted to the fender apron. I've run across cars where the the Yellow #37C was on the terminal block and #38 on the starter relay - which essentially bypasses the ammeter (#654 & 655)

1709135931685.png
 

Attachments

  • HOW ALTERNATORS WORK.pdf
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The difference is in how the regulator is controlled. A non-gauge car uses the warning light circuit (Green w/red stripe #904) through the I terminal to energize the alternator field coil, and the stator output (White w/Black stripe) through the S terminal then closes the field relay in the regulator. A gauge car has that circuit, minus the warning light, but it is wired through the S terminal to the field relay inside the regulator, and battery voltage (Yellow w/white dots #36) through the A terminal then energizes the alternator field coil.

View attachment 86137

If you want to get into the weeds, download the PDF attachment below. Some of the circuit numbers may not match as the author has a '69.

If the ammeter doesn't move at all, I've sometimes found them to be wired incorrectly. Both the Black w/Orange stripe from the alternator (#38A) and the Black w/Orange stripe from the main harness (#38) must be on the terminal block mounted to the fender apron. I've run across cars where the the Yellow #37C was on the terminal block and #38 on the starter relay - which essentially bypasses the ammeter (#654 & 655)

View attachment 86136
That could be what I have going on that second thingy you said. I’ll get a puc soon and see as always Thanks!!
 
That could be what I have going on that second thingy you said. I’ll get a pic soon and see as always Thanks!!
Here are pics of how my connections are. I did move alternator wire over to the terminal block and can see the needle move ever so slightly. I have not put it back to see if it moves ever so slightly the way I had it before. I’m not sure where the needle should sit and how much or if it should move when turning the key on and then starting it. I did try turning on the blower motor full blast and the lights at the same time and the needle moved slightly. The needle sits about a half needle width to the left of the center mark. When running it will go just barely past center. It could have been this way with the way I had the wires connected before and just never noticed that slight movement. What does the light green with red stripe do on a gauge car?
My new alt harness has a connection for it and I tried it with and without it hooked up.
Thanks IMG_0625.jpegIMG_0626.jpegIMG_0627.jpegIMG_0628.jpegIMG_0629.jpeg
 
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The ammeter on all Mustangs from 66 through 73 barely move in the best of conditions. If yours deflects ever so slightly, then it is working. To test, key in ACC, headlights on, doors open, foot on brake, cigarette lighter on and maybe it will deflect a half needle's width. Consider that gauge the equivalent of an alternator indicator lamp, in that it will be either way left or right if there is a significant issue, or centered for normal operation.
You threw me off by using the term alt gauge. Whenever I see alternator or alt, I think of the indicator lamp system. The correct term for that gauge is an ammeter gauge.
 
The ammeter on all Mustangs from 66 through 73 barely move in the best of conditions. If yours deflects ever so slightly, then it is working. To test, key in ACC, headlights on, doors open, foot on brake, cigarette lighter on and maybe it will deflect a half needle's width. Consider that gauge the equivalent of an alternator indicator lamp, in that it will be either way left or right if there is a significant issue, or centered for normal operation.
You threw me off by using the term alt gauge. Whenever I see alternator or alt, I think of the indicator lamp system. The correct term for that gauge is an ammeter gauge.
Thanks Midlife I really appreciate it. These little things can keep you up at night. 🤪
 
Here are pics of how my connections are. I did move alternator wire over to the terminal block and can see the needle move ever so slightly. I have not put it back to see if it moves ever so slightly the way I had it before. I’m not sure where the needle should sit and how much or if it should move when turning the key on and then starting it. I did try turning on the blower motor full blast and the lights at the same time and the needle moved slightly. The needle sits about a half needle width to the left of the center mark. When running it will go just barely past center. It could have been this way with the way I had the wires connected before and just never noticed that slight movement. What does the light green with red stripe do on a gauge car?
My new alt harness has a connection for it and I tried it with and without it hooked up.

You need to move the black lead from the starter solenoid to the terminal block with the Black W/Orange wire. Right now you are essentially bypassing the ammeter.

Your green wire is the Heavy Yellow #37C, it appears to have been repaired with an aftermarket fusible link.

1711567916895.png
 

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