Alternator wiring issues

[7duce swinger]

Hi Fabo I am not sure my alternator is wired correctly. Could be or could just be a bad alternator. I have a purple wire coming from the harness but goes to nothing. Sold the car in 2011 I believe and I purchased it back in 2017. Came wired like this.

Does anyone know where the purple wire goes too and if my alternator should be grounded like it is? I figured touching the motor is the same ground lol.

 

[Dana67Dart]

1. what car?
2. What year?
3. what modifications?
4. do you have 1 wire field (round back) alt or 2 wire Square back? (IIRC)
5. is your voltage regulator new style for 2 wire field ( 3 prong triangular connector on regulator) or 1 wire for round (screw lug and single slip on connector?

 

[barracudadave67]

Purple wire is for factory temp sensor.
Dave

 

[7duce swinger]

1. what car?
2. What year?
3. what modifications?
4. do you have 1 wire field (round back) alt or 2 wire Square back? (IIRC)
5. is your voltage regulator new style for 2 wire field ( 3 prong triangular connector on regulator) or 1 wire for round (screw lug and single slip on connector?

1972 swinger small block, cam, heads, supercharged.

It is the square back two fields

 

[pt70]

1972 swinger small block, cam, heads, supercharged.

'7' ; the large red wire on the alternator output appears to go to a ground on the fender. If so, this is wrong. It should be a #10 black wire going into the center section of the bulkhead connector. Then go to the ammeter, out the other ammeter terminal, back thru the bulkhead connector, then to the starter relay on the left fender. Do all wiring work with the battery negative terminal disconnected. Before reconnecting the battery, close the doors and test the current draw with a test light.

 

[Mattax]

the large red wire on the alternator output appears to go to a ground on the fender. If so, this is wrong. It should be a #10 black wire going into the center section of the bulkhead connector. Then go to the ammeter, out the other ammeter terminal, back thru the bulkhead connector, then to the starter relay on the left fender. Do all wiring work with the battery negative terminal disconnected. Before reconnecting the battery, close the doors and test the current draw with a test light.

It sure looks like that in photo!
Could be an insulated stud, from which it could have one wire to the ammeter and a seperate wire to the main splice. Hard to know without seeing more.

It is the square back two fields

All that "two field" means is that it has two insulated field terminals instead of one grounded terminal.
In the photo we see a wire from each leading back to the firewall. So it should have the voltage regulator with the triangular connector. (#5) in Dana's list.

Dave above says the light purple in the back goes to the temperature sender. So maybe that's it.
Get '72 Service manual. That will be the most accurate way to ID any color & wire size and position in the bulkhead other than an expert familiar with that year.
Some colors and sizes stayed the same for many years, but not all.

 

[7duce swinger]

It sure looks like that in photo!
Could be an insulated stud, from which it could have one wire to the ammeter and a seperate wire to the main splice. Hard to know without seeing more.


All that "two field" means is that it has two insulated field terminals instead of one grounded terminal.
In the photo we see a wire from each leading back to the firewall. So it should have the voltage regulator with the triangular connector. (#5) in Dana's list.

Dave above says the light purple in the back goes to the temperature sender. So maybe that's it.
Get '72 Service manual. That will be the most accurate way to ID any color & wire size and position in the bulkhead other than an expert familiar with that year.
Some colors and sizes stayed the same for many years, but not all.

Sorry but does not matter what it looks like. It is going to the ground on the alternator.

You arent telling me anything new other than what he has already stated lol.

 

[7duce swinger]

Thank you, I will try that now. Have no idea why they put the ground from fender to the alternator "gnd" it was like that when I bought it back from someone on craigslist. Use to be mine in 2009-2010. I'm just left fixing all the issues on it.

 

[7duce swinger]

Theoretically, the car should stay on with battery terminal taken off correct? It is turning off as soon as battery terminal is disconnected.

I am going to see the amperage draw and try to keep checking what needs to be done.

 

[67Dart273]

Theoretically, the car should stay on with battery terminal taken off correct? It is turning off as soon as battery terminal is disconnected.

I am going to see the amperage draw and try to keep checking what needs to be done.

DO NOT EVER DO THIS. NEVER EVER

This is a flawed test, and is in fact NOT even a test. You will NEVER see this "test" in any textbook. And, it proves nothing

 

[7duce swinger]

It sure looks like that in photo!
Could be an insulated stud, from which it could have one wire to the ammeter and a seperate wire to the main splice. Hard to know without seeing more.


All that "two field" means is that it has two insulated field terminals instead of one grounded terminal.
In the photo we see a wire from each leading back to the firewall. So it should have the voltage regulator with the triangular connector. (#5) in Dana's list.

Dave above says the light purple in the back goes to the temperature sender. So maybe that's it.
Get '72 Service manual. That will be the most accurate way to ID any color & wire size and position in the bulkhead other than an expert familiar with that year.
Some colors and sizes stayed the same for many years, but not all.

As far as what you're saying there doesnt appear to be any wire going to starter relay. Have no idea what's going on with my working at the moment. When I first got it back the guy had everything wired to 12v lol.

 

[7duce swinger]

DO NOT EVER DO THIS. NEVER EVER

This is a flawed test, and is in fact NOT even a test. You will NEVER see this "test" in any textbook. And, it proves nothing

Maybe not a text book but it works at the very minimum. I just wanted to see if the alternator was doing its job.

What is the real test?

 

[7duce swinger]

It sure looks like that in photo!
Could be an insulated stud, from which it could have one wire to the ammeter and a seperate wire to the main splice. Hard to know without seeing more.


All that "two field" means is that it has two insulated field terminals instead of one grounded terminal.
In the photo we see a wire from each leading back to the firewall. So it should have the voltage regulator with the triangular connector. (#5) in Dana's list.

Dave above says the light purple in the back goes to the temperature sender. So maybe that's it.
Get '72 Service manual. That will be the most accurate way to ID any color & wire size and position in the bulkhead other than an expert familiar with that year.
Some colors and sizes stayed the same for many years, but not all.

This is what I got going on, sorry didnt have access to the car til now to post ant other pictures.

 

[7duce swinger]

Where do these wires go

 

[AJ/FormS]

on a Mopar you don't need an alternator case ground; in 50 years I don't think I have ever seen anything connected to that stud.But I gotta tell ya, there is something weird about that case. It looks left handed.

As for the device in post 14, IDK

 

[7duce swinger]

on a Mopar you don't need an alternator case ground; in 50 years I don't think I have ever seen anything connected to that stud.But I gotta tell ya, there is something weird about that case. It looks left handed.

Yeah it wasnt connected when I had it and sold it way back when. But I have no idea why he did it this time.

As for the device in post 14, IDK

on a Mopar you don't need an alternator case ground; in 50 years I don't think I have ever seen anything connected to that stud.But I gotta tell ya, there is something weird about that case. It looks left handed.

As for the device in post 14, IDK

 

[Mattax]

This is what I got going on, sorry didnt have access to the car til now to post ant other pictures.

View attachment 1715394915

No problem.
Looks like we have some non-standard color choices.
Lets start with the easy to identify.

Ground stud on alternator housing. Heavy Red wire to fender.
The use of a supplementary ground is usually not needed.
However, its possible this is the only ground between the engine and body. Stock is usually a block wire from back engine ot firewall.
Additionally if the battery has been moved to the trunk, additional grounding would be helpful. Bassically it can't hurt. Only danger is that it has red insulation and people assume red are hot wires.

Field terminals. Each one is attached to a carbon brush to contacts the copper rings of the rotor. You can see the one ring and the white insulation in the photo.
When electricity flows through the windings of the rotor an electromagnetic field is created. Field is shorthand for electromagnetic field.

'72 would use a voltage regulator with a triangular plug.
This \/ appears to be an emmissions related switch that was picking up outside air temperature coming through the cowl.

I don't think its related to anything with the way the car is now setup.

Output stud.
This should have a heavy wire, 12 or 10 gage, going to through the firewall to the main splice. At least that would be the original setup.

 

[Mattax]

The field wires, and output wire were originally hooked up something like this.

Alternatively you could run the output wire like the '73 60 amp alternator cars were done. I've posted that here before so a search will turn that up.
The wires in your hand you'll have to look up in a '72 FSM and/or '72 Master Tech booklets at the Imperial Club or Mymopar.

 

[Mattax]

As far as what you're saying there doesnt appear to be any wire going to starter relay. Have no idea what's going on with my working at the moment. When I first got it back the guy had everything wired to 12v lol.

Starter relay???
Who mentioned starter relay?
Or are you saying there's no battery feed either?
Well that can't be cause you just told us the engine is working.

 

[7duce swinger]

No problem.
Looks like we have some non-standard color choices.
Lets start with the easy to identify.
View attachment 1715394952

Ground stud on alternator housing. Heavy Red wire to fender.
The use of a supplementary ground is usually not needed.
However, its possible this is the only ground between the engine and body. Stock is usually a block wire from back engine ot firewall.
Additionally if the battery has been moved to the trunk, additional grounding would be helpful. Bassically it can't hurt. Only danger is that it has red insulation and people assume red are hot wires.

Field terminals. Each one is attached to a carbon brush to contacts the copper rings of the rotor. You can see the one ring and the white insulation in the photo.
When electricity flows through the windings of the rotor an electromagnetic field is created. Field is shorthand for electromagnetic field.

'72 would use a voltage regulator with a triangular plug.
This \/ appears to be an emmissions related switch that was picking up outside air temperature coming through the cowl.
View attachment 1715394957

I don't think its related to anything with the way the car is now setup. Power wire on alt is

Output stud.
This should have a heavy wire, 12 or 10 gage, going to through the firewall to the main splice. At least that would be the original setup.

Yes that is exactly how the alt is setup. Heavy wire on power output stud.

 

[7duce swinger]

Starter relay???
Who mentioned starter relay?
Or are you saying there's no battery feed either?
Well that can't be cause you just told us the engine is working.
View attachment 1715394966

Post #5 mentions starter relay... accidentally quoted you instead of the original commentor lol
Car does turn on and run, just drains batt

 

[7duce swinger]

So I have the correct voltage regulator for the setup?

 

[7duce swinger]

Bump

 

[oldkimmer]

Is there a heavy black wire on the battery stud on the alt? Kinda looks like it’s missing. Kim

 

[67Dart273]

Maybe not a text book but it works at the very minimum. I just wanted to see if the alternator was doing its job.

What is the real test?

This is not a test and can cause damage, and here is why it is NOT a test:

"Let's say" the thing is partially charging, maybe has a couple of bad diodes, so your 45A alternator is now a "20A" alternator. You take off the battery cable and it still runs and you INcorrectly assume it is OK. When it is only putting out barely enough to run the engine

"Let's say" there is actually nothing at all wrong with the charging system, and you unhook the cable, it dies, and you INcorrectly assume it is bad. "Might be" it was just idling too slow.

DAMAGE. WHEN YOU UNHOOK a battery with a working charging system, this causes a voltage spike that is sometimes WAY over a safe level, and can damage electronics, especially in this age of EFI, solid state stereo, on and on.

MORE

FIRST determine what the wiring is doing and hooked to. I tend to dived problems into (no particular order)

The output/ charging line, that is, the wiring from the alternator output stud, thorugh the bulkhead, ammeter, back through the bulkhead, and to the battery

The field wiring, IE the wiring from the ignition switch to the volt. regulator, the VR ground, the wiring to the alternator field (70 and later) and so on

The components, the VR, the alternator, the battery

TO TEST: First determine if the alternator can output current, eliminating some of the wiring, and the VR. And, determine if the charge line is actually connected to the battery

DO DO THIS. "Rig" alligator clip/ other/ jumper wires. Disconnect the "push on" wires to the alternator field and "safe" them off, tape, etc. Rig a jumper to ground from one alternator field connection. Does not matter which. Rig a jumper from the remaining alternator field to the battery. When you connect/ disconnect the wire in subdued lighting, you should see a small spark.

Monitor the alternator output stud with a voltmeter. Run the engine slowly up in RPM. The voltage should rise from resting battery voltage (it may vary depending on state of battery charge) from something below 12 up through 12.6. When running, and RPM increased, voltage should rise. Do not allow it to go above say, 16V or so

IF THE output stud voltage goes WAY high, say, 20+V, move the meter to the battery and compare. If it does not "follow" and is fairly low---then you have a lot of resistance in the charging wire path, bad connection, etc

IF THE output does not rise, and remains the same as the resting battery, then the alternator is NOT charging. Find out why, or replace the alternator. First thing I'd do in that case is check the brushes. May simply be worn down