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1973 Mustang Alternator Applications
#1
runninpony 
The alternators used in 1973 Mustangs have always been a point of confusion for me. The Ford schematics and shop manuals show 42 amp, 55 amp, 61 amp, and 70 amp alternators as applicable parts for a 1973 Mustang. The 70 amp alternator is unique in that it has a different configuration for the wire harness. One would think that a low optioned six cylinder car might have received the 42 amp version and that a highly optioned V8 would get the 70 amp model. I have a Mach 1 with a 70 amp alternator (has power windows and rear window defrost). Another member of this forum, jeff8877, has a highly optioned Mach 1 and it appears that his came with a 55 amp alternator. There are people out there that say the 70 amp alternator was not used on the Mustang at all. There are a few members on this forum that have 70 amp alternators that I know of. Unfortunately, the Marti report or the Emminger invoice did not mention anything about alternator choices. I have the original order form for my 4 speed car and it makes no mention of a specific alternator type. That leads me to believe that the alternator choice was made based on the options that the car had installed at the factory. I presume that the vast majority of the 1973 Mustangs came with the 55 amp alternator. I am interested in hearing from any forum members on this topic - what alternator do you have with which options? If you have a 70 amp alternator, do you also have rear window defrost and/or power windows? Do you have a 55 amp alternator with power windows or rear window defrost? Does anyone have a 42 amp or a 61 amp alternator? I will attempt to digest all of the inputs and try to understand what rationale was used during assembly of these cars. If you know your build date, please supply that as well. In addition, if you have your build sheet, check row D, character positions 16 and 17 for the alternator code used on your car. Hopefully with enough inputs we can figure out what parameters were in place to determine alternator size for these cars.

Steve
73 Mach 1 Blue Glow/Argent Q Code C6 Auto
73 Mach 1 Blue Glow/Argent Q Code 4 Speed
  Reply
#2
Steve73QMach1;160029 Wrote:The alternators used in 1973 Mustangs have always been a point of confusion for me The Ford schematics and shop manuals show 42 amp, 55 amp, 61 amp, and 70 amp alternators as applicable parts for a 1973 Mustang. The 70 amp alternator is unique in that it has a different configuration for the wire harness. One would think that a low optioned six cylinder car might have received the 42 amp version and that a highly optioned V8 would get the 70 amp model. I have a Mach 1 with a 70 amp alternator (has power windows and rear window defrost). Another member of this forum, jeff8877, has a highly optioned Mach 1 and it appears that his came with a 55 amp alternator. There are people out there that say the 70 amp alternator was not used on the Mustang at all. There are a few members on this forum that have 70 amp alternators that I know of. Unfortunately, the Marti report or the Emminger invoice did not mention anything about alternator choices. I have the original order form for my 4 speed car and it makes no mention of a specific alternator type. That leads me to believe that the alternator choice was made based on the options that the car had installed at the factory. I presume that the vast majority of the 1973 Mustangs came with the 55 amp alternator. I am interested in hearing from any forum members on this topic - what alternator do you have with which options? If you have a 70 amp alternator, do you also have rear window defrost and/or power windows? Do you have a 55 amp alternator with power windows or rear window defrost? Does anyone have a 42 amp or a 61 amp alternator? I will attempt to digest all of the inputs and try to understand what rationale was used during assembly of these cars. If you know your build date, please supply that as well. In addition, if you have your build sheet, check row D, character positions 16 and 17 for the alternator code used on your car. Hopefully with enough inputs we can figure out what parameters were in place to determine alternator size for these cars.

Steve,
So you have a GPD alternator with side terminals? I know mine has the rear terminals so I'll have to dig it out to find out the Amps. The alternators have color codes for the rear connection ones.
Orange = 42 A
Red = 55A
Green =61A

My build sheet as a code of 5B for my car.
-jbojo

-john
(jbojo)
351C 4V cc heads, 10.5 : 1 CR, 290 Herbert cam, Flat top forged pistons, forged connecting rods, Atomic efi,
C6 with Gear Vendor overdrive, 3.89 Tru Trac, Hooker Super Comp with 2 1/2" Pypes Exhaust.        

Some Mod pictures can be seen at:

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#3
I posted on the other thread before I saw this one. My '73 has code 7A on the build sheet. The alternator does not look original so I do not think anything on the case will be of much use. With the rear defrost, I should have had a higher amp alternator.

[Image: 1673if.png]
50 F1
73 Mach 1
86 F150
96 F150
2014 F150
Always looking
  Reply
#4
Mine is a q code with no a/c , no rear window defrost,and no power windows. I can't read my build sheet, but I have a red wire going to my alt so I guess it's a 55 amp.

Jay
73 mach1
  Reply
#5
jbojo...

The color codes you mentioned...are those paint marks on back of alt or different wire colors or different color insulators on alt?

The alternators have color codes for the rear connection ones.
Orange = 42 A
Red = 55A
Green =61A

Jeff
  Reply
#6
jeff8877;160063 Wrote:jbojo...

The color codes you mentioned...are those paint marks on back of alt or different wire colors or different color insulators on alt?

The alternators have color codes for the rear connection ones.
Orange = 42 A
Red = 55A
Green =61A

Jeff

Jeff not sure, I pulled the color codes from the service manual for 73. I'll go out and dig up my alternator and see if it has color codes on it. I do not believe that those are the wire colors.
-jbojo

-john
(jbojo)
351C 4V cc heads, 10.5 : 1 CR, 290 Herbert cam, Flat top forged pistons, forged connecting rods, Atomic efi,
C6 with Gear Vendor overdrive, 3.89 Tru Trac, Hooker Super Comp with 2 1/2" Pypes Exhaust.        

Some Mod pictures can be seen at:

  Reply
#7
Steve,

73 Mach Q code
Build Date...6/12/73
High draw options...A/C, power windows, rear defrost
Build sheet...not legible
Alternator harness...rear mount type
Alternator...original unknown
Volt Reg Part #...original unknown
Trans...C6 auto

Jeff
  Reply
#8
jbojo;160072 Wrote:
jeff8877;160063 Wrote:jbojo...

The color codes you mentioned...are those paint marks on back of alt or different wire colors or different color insulators on alt?

The alternators have color codes for the rear connection ones.
Orange = 42 A
Red = 55A
Green =61A

Jeff

Jeff not sure, I pulled the color codes from the service manual for 73. I'll go out and dig up my alternator and see if it has color codes on it. I do not believe that those are the wire colors.
-jbojo

Jeff,

According to some documentation I found, those colors were inked on the back of the alternator for ID purposes. the 70 amp alternators received no color code. The amp rating of the alternator was also impression stamped on the case. jbojo is correct - they are not the wire colors.

jbojo;160047 Wrote:
Steve73QMach1;160029 Wrote:The alternators used in 1973 Mustangs have always been a point of confusion for me The Ford schematics and shop manuals show 42 amp, 55 amp, 61 amp, and 70 amp alternators as applicable parts for a 1973 Mustang. The 70 amp alternator is unique in that it has a different configuration for the wire harness. One would think that a low optioned six cylinder car might have received the 42 amp version and that a highly optioned V8 would get the 70 amp model. I have a Mach 1 with a 70 amp alternator (has power windows and rear window defrost). Another member of this forum, jeff8877, has a highly optioned Mach 1 and it appears that his came with a 55 amp alternator. There are people out there that say the 70 amp alternator was not used on the Mustang at all. There are a few members on this forum that have 70 amp alternators that I know of. Unfortunately, the Marti report or the Emminger invoice did not mention anything about alternator choices. I have the original order form for my 4 speed car and it makes no mention of a specific alternator type. That leads me to believe that the alternator choice was made based on the options that the car had installed at the factory. I presume that the vast majority of the 1973 Mustangs came with the 55 amp alternator. I am interested in hearing from any forum members on this topic - what alternator do you have with which options? If you have a 70 amp alternator, do you also have rear window defrost and/or power windows? Do you have a 55 amp alternator with power windows or rear window defrost? Does anyone have a 42 amp or a 61 amp alternator? I will attempt to digest all of the inputs and try to understand what rationale was used during assembly of these cars. If you know your build date, please supply that as well. In addition, if you have your build sheet, check row D, character positions 16 and 17 for the alternator code used on your car. Hopefully with enough inputs we can figure out what parameters were in place to determine alternator size for these cars.

Steve,
So you have a GPD alternator with side terminals? I know mine has the rear terminals so I'll have to dig it out to find out the Amps. The alternators have color codes for the rear connection ones.
Orange = 42 A
Red = 55A
Green =61A

My build sheet as a code of 5B for my car.
-jbojo

Yes - I have the side terminal GPD 70 amp alternator described in Part 31-12 of the 1973 Ford Shop manual. It is interesting that the amp rating on all of the alternators except 70A is at 15V and 2900 RPM. The 70 amp alternator is 15V and 5000 RPM. Maybe the transmission type is also a player here. My car is a 4 speed.

Steve
73 Mach 1 Blue Glow/Argent Q Code C6 Auto
73 Mach 1 Blue Glow/Argent Q Code 4 Speed
  Reply
#9
Sorry, I thought it was wire colors, mine has been replaced with a motorcraft but no part numbers that i can find.

Jay
73 mach1
  Reply
#10
Steve,

After a quick look, I do have the side pole alternator and the wiring has not been messed with to the best of my knowledge - so probably a 70 amp according to the shop manual. Add that to the 7A on the build sheet.

[Image: 1673if.png]
50 F1
73 Mach 1
86 F150
96 F150
2014 F150
Always looking
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