Electrical Alternator wiring

Ed88 · Jan 5, 2021

1974 v6 engine
I've changed everything I can think of but the the charging system still won't work. Does anyone have a wiring diagram for the charging system? I'm used to there being a wire to the battery from the alternator or something and there's doesn't seem to be anything like that on here. Nothing has been rewired or anything from what I can tell.

extra_stout · Jan 5, 2021

The alternator doesn't make big current, because of that there is just a small sized wire to the battery, which is integrated to the loom. Modern alternators have the regulator integrated, old ones like yours have a separate regulator, which you can find on the driver side engine bay.
If you changed everything else (the alternator itself?!), most likely your regulator will be damaged?!

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LILCBRA · Jan 6, 2021

Have you added any kind of electrical draw on the system? These systems were just above adequate for their time.

I ran into issues with my car late last summer. I added an AF gauge and wired the lights for my other auxiliary gauges. That was enough for my system to not produce enough to keep my battery charged while running with the headlights at night. I upgraded to a 3G alternator from a later model Ford and haven't had any issues with the charging system since. Here is the thread for my install: https://www.stangnet.com/mustang-forums/threads/mo-powah.917796/

Ed88 · Jan 6, 2021

I've had this issue the entire time I've owned the car (going on 3 years). I have added an electric fuel pump in the past 4 months but thats all. Other than that its all stock.

extra_stout said:
The alternator doesn't make big current, because of that there is just a small sized wire to the battery, which is integrated to the loom. Modern alternators have the regulator integrated, old ones like yours have a separate regulator, which you can find on the driver side engine bay.
If you changed everything else (the alternator itself?!), most likely your regulator will be damaged?!

1974 FORD MUSTANG II 2.8L 171cid V6 Voltage Regulator | Shop Now at RockAuto

Electrical Parts and More for Your 1974 FORD MUSTANG II at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

Don't buy a cheap one. Even the more expensive ones fail...

I have changed the regulator too. I can tell you how many alternators, batteries and regulators I've put in the car. I havent seen any small wire back to the battery.

LILCBRA said:
Have you added any kind of electrical draw on the system? These systems were just above adequate for their time.

I ran into issues with my car late last summer. I added an AF gauge and wired the lights for my other auxiliary gauges. That was enough for my system to not produce enough to keep my battery charged while running with the headlights at night. I upgraded to a 3G alternator from a later model Ford and haven't had any issues with the charging system since. Here is the thread for my install: https://www.stangnet.com/mustang-forums/threads/mo-powah.917796/

I was actually looking for an upgrade. The weird thing is I can't even get good volts out of the alternator for a multimeter. Even with a brand new alternator it won't push volts at any rpm.

Adieu · Jan 6, 2021

I'm with @LILCBRA , the archaic, externally-regulated alternators on these cars were barely adequate when new 47 years ago, and with wiring that old combined with the inferior quality of the replacements parts out of China and Mexico to service them, you're better off upgrading to something better.

The 3G Ford alternator is a good upgrade, as is going to a GM CS-style or one-wire alternator (or going with an aftermarket Ford 1-wire from someone like Powermaster).

extra_stout · Jan 6, 2021

Ed88 said:
I havent seen any small wire back to the battery.

The yellow-white wire from the regulator is connected inside the loom to other wires. I had the loom apart... The regulator is connected to the alternator by a orange-lightblue wire.
There are descriptions how to check the regulator and the alternator. I'm not so much into the electrical stuff, but even when you want to upgrade to a 3g alternator, you need at least voltage at the lightgreen-red cable at the regulator from the ignition switch (when ignition is on).
@MustangIIMatt has better understanding than I do, but from my experience with my 66 coupe the stock system can run fine, even when it is old. But if you changed alternator and regulator, perhaps you have issues with a bad wire. In my opinion if you have new parts allready installed I would try to get them working. I would check with a multimeter if the wire from alternator to the regulator has a connection. Than: if the lightgreen-red cable from the igniton switch shows voltage when ignition on.
I would then check, if there is a connection between the regulator and the battery/starter solenoid.

Ed88 · Jan 6, 2021

@LILCBRA

extra_stout said:
The yellow-white wire from the regulator is connected inside the loom to other wires. I had the loom apart... The regulator is connected to the alternator by a orange-lightblue wire.
There are descriptions how to check the regulator and the alternator. I'm not so much into the electrical stuff, but even when you want to upgrade to a 3g alternator, you need at least voltage at the lightgreen-red cable at the regulator from the ignition switch (when ignition is on).
@MustangIIMatt has better understanding than I do, but from my experience with my 66 coupe the stock system can run fine, even when it is old. But if you changed alternator and regulator, perhaps you have issues with a bad wire. In my opinion if you have new parts allready installed I would try to get them working. I would check with a multimeter if the wire from alternator to the regulator has a connection. Than: if the lightgreen-red cable from the igniton switch shows voltage when ignition on.
I would then check, if there is a connection between the regulator and the battery/starter solenoid.

I'll definitely check into those connections.

Ed88 · Jan 6, 2021

MustangIIMatt said:
I'm with @LILCBRA , the archaic, externally-regulated alternators on these cars were barely adequate when new 47 years ago, and with wiring that old combined with the inferior quality of the replacements parts out of China and Mexico to service them, you're better off upgrading to something better.

The 3G Ford alternator is a good upgrade, as is going to a GM CS-style or one-wire alternator (or going with an aftermarket Ford 1-wire from someone like Powermaster).

I was thinking of a one wire but I honestly am not sure how to do that. But I have an 02 v6 mustang and I can pull the alternator off that and do the 3g conversion. I just hope it helps. I love this car but damn is this issue annoying

LILCBRA · Jan 6, 2021

Kinda sounds like you possibly have 2 issues. Does the battery die if left unattended for a few days? If so, it could be a bad circuit somewhere. And, if that's the case, combine that with the added draw of the electric pump and I'm sure your alternator just can't keep up.

Ed88 · Jan 6, 2021

If it sits it doesn't usually lose any juice. But I had this problem before adding the pump to the car. I did have some bad light sockets on the tail lamps but those have been replaced. Even so I wouldnt think those wouldn't effect the charging system

LILCBRA · Jan 6, 2021

Ed88 said:
If it sits it doesn't usually lose any juice. But I had this problem before adding the pump to the car. I did have some bad light sockets on the tail lamps but those have been replaced. Even so I wouldnt think those wouldn't effect the charging system

I guess it depends on whether they had power to them or not (i.e. night driving or braking). If they were corroded or whatever it will take more power to light the bulbs. And if more than just those sockets were corroded or bad, multiply the problem by that many sockets. A lot of small draws will add up. Not saying that's the problem, but I'm sure it contributes.

It sounds like you have a drain somewhere when the key is in the "Run" position. About the only way you're going to be able to track that down is to start pulling fuses one at a time and checking the amp draw at the battery when the key is in the "Run" position. There are a number of videos and websites that outline the process, like this one for example: ( https://www.yourmechanic.com/article/how-to-diagnose-a-car-battery-drain_2 ). I can't help much more than that, though. Beyond this my suggestion is to upgrade the system as I did or as @MustangIIMatt suggested with a one wire alternator. Maybe Matt or one of the other guys can give another suggestion that I'm not thinking of?

Ed88 · Jan 6, 2021

LILCBRA said:
I guess it depends on whether they had power to them or not (i.e. night driving or braking). If they were corroded or whatever it will take more power to light the bulbs. And if more than just those sockets were corroded or bad, multiply the problem by that many sockets. A lot of small draws will add up. Not saying that's the problem, but I'm sure it contributes.

It sounds like you have a drain somewhere when the key is in the "Run" position. About the only way you're going to be able to track that down is to start pulling fuses one at a time and checking the amp draw at the battery when the key is in the "Run" position. There are a number of videos and websites that outline the process, like this one for example: ( https://www.yourmechanic.com/article/how-to-diagnose-a-car-battery-drain_2 ). I can't help much more than that, though. Beyond this my suggestion is to upgrade the system as I did or as @MustangIIMatt suggested with a one wire alternator. Maybe Matt or one of the other guys can give another suggestion that I'm not thinking of?

I'll look into doing that. I dont suppose you have a picture of how the stock ignition solenoid is wired?
Thats the only thing that was replaced by the "buddy" I bought it from. And let's just say he isn't that great of a wrench turner.

LILCBRA · Jan 6, 2021

Ed88 said:
I'll look into doing that. I dont suppose you have a picture of how the stock ignition solenoid is wired?
Thats the only thing that was replaced by the "buddy" I bought it from. And let's just say he isn't that great of a wrench turner.

Seems like I shared this somewhere a while back, but here's a pictogram.

Potomus Pete · Jan 6, 2021

Is the car supposed to run any differently with the stronger alternator ?

LILCBRA · Jan 6, 2021

Potomus Pete said:
Is the car supposed to run any differently with the stronger alternator ?

No, it should run as it should regardless of the size of the alternator as long as the alternator can supply enough juice for the engine to run properly.

Ed88 · Jan 7, 2021

LILCBRA said:
Seems like I shared this somewhere a while back, but here's a pictogram.

Yeah I dont think mine is like that. Ill post a pic after work

Ed88 · Jan 7, 2021

LILCBRA said:
Seems like I shared this somewhere a while back, but here's a pictogram.

Yeahhhh mine looks different

LILCBRA · Jan 7, 2021

As long as it starts the car it's most likely fine. All it really is is an on/off switch for the starter. When the key is turned it sends current to the solenoid and the plunger inside moves the opposite direction closing the full 12v circuit to the starter.

Ed88 · Jan 7, 2021

Thats what I figured.
What has me so puzzled about my charging issue is I've had multiple people say that there should be a wire from the alternator the the battery. But every wiring diagram I've seen doesn't show one. I dont even get more than 12v out of a brand new alternator. Its just so weird to me. I did order that 1g to 3g kit you suggested and im gonna pull the known good alternator out of my 02 v6 to give it a whirl.

LILCBRA · Jan 7, 2021

@MustangIIMatt can correct me if I'm wrong since I'm going from memory, but it seems an alternator should put out around 13-14 volts, but I think that's at capacity. At idle it probably isn't putting out quite that much. So if it's working as it should, and it sounds like it's possible that it is, the charging problem isn't with the voltage it's putting out but the amperage. That's where the 3G comes in. As referenced in that article in my thread, the original 1G alternator only puts out 60 amps on a good day, the 3G puts out 130ish, so over 2x what the 1G does. And that's the small 3G - there are bigger versions available. So if your car is pulling, let's say 65 amps, and your alternator is only putting out 60 amps max, your battery will drain. Switching to the 3G will eliminate the problem altogether as long as it's installed properly. Good luck and let us know how it works for you!

Electrical Alternator wiring

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