Charging Issue

-

archerandethansdad

Well-Known Member
Joined
Jul 11, 2021
Messages
47
Reaction score
9
Location
MD
Hello Everyone, I am having an issue with my car not charging. I replaced the alternator when i first purchased the car as long as the regulator which had a poor ground and fried. This was about 4 months ago and it's been fine since. However now it won't charge. I'm getting battery voltage at the alternator with key off. Key on i'm getting .10 on the field. Single post by the way. Also .10 at the regulator. I jumped the field wire on the alternator to negative post on battery and nothing. So i take it off and run to advanced and have them test it and it comes back good. So i swap the regulator and still nothing. Same thing test my posts and same results. Jump the alternator and nothing. I'm kind of stumped. Also just swapped alternator today under warranty and still same thing.
 
Single post by the way.
So you have some sort of Chrysler built vehicle with a grounded brush alternator. So we can guess its a pre-1970.
Is this correct?
See here for what is a grounded brush alternator: Identifying Chrysler Alternators (1960-1976)

However now it won't charge
I'm going to just assume nothing at the point, so my apologies for the questions.
When the engine is running what does needle on the gage labled 'alternator' do?
does it change between idle and say fast idle?

and if you know from using your multimeter:
What does the voltage across the battery read with the engine running?
What is the voltage at the alternator output terminal (the stud) ?



I'm getting battery voltage at the alternator with key off.
It should always be the same, key on, key off, engine running, engine not running. Both of those wires (battery positive and alternator output) are welded together under the dash.

Key on i'm getting .10 on the field.
Also .10 at the regulator.
Not sure what you are measuring here. volts to ground?
If the ignition side of the regulator is not getting power with the key on (should show same voltage as battery) then there is a bad connection between the regulator ignition terminal and the key switch. This is assuming there is a good connection to the key switch from the battery and the alternator.
 
Last edited:
First and foremost...
What car?
What year?
Post photos of the front and back of your alternator
Post photos of your voltage regulator

Then....

I jumped the field wire on the alternator to negative post on battery and nothing
Assuming the alternator is properly wired as a 1 field wire alternator, grounding the 1 field wire terminal on the alternator would produce no charging from the alternator.

If you ground the 1 field wire from the voltage regulator you will burn out the voltage regulator.

Some simple tests
With the engine running, measure voltage from battery negative to the following points
  1. Input to the voltage regulator
  2. Output from the voltage regulator
  3. Input to the field terminal on the altrnator
  4. Output from the alternator charge post
  5. Positive post on the battery
Record the values and report back
 
Not sure what you are measuring here. volts to ground?
If the ignition side of the regulator is not getting power with the key on (should show same voltage as battery) then there is a bad connection between the regulator ignition terminal and the key switch. This is assuming there is a good connection to the key switch from the battery and the alternator.

Concentrate on ^^this^^ here. have you recently made changes to the ignition system? There is only one wire coming through the bulkhead connector that supplies underhood loads in the key "run" position. THIS IS NOT FUSED. Depending on the year, the dark blue (usually) "ignition run" wire feeds ignition system, VR, electric choke if used, smog devices if used, etc.
 
First and foremost...
What car?
What year?
Post photos of the front and back of your alternator
Post photos of your voltage regulator

Then....


Assuming the alternator is properly wired as a 1 field wire alternator, grounding the 1 field wire terminal on the alternator would produce no charging from the alternator.

If you ground the 1 field wire from the voltage regulator you will burn out the voltage regulator.

Some simple tests
With the engine running, measure voltage from battery negative to the following points
  1. Input to the voltage regulator
  2. Output from the voltage regulator
  3. Input to the field terminal on the altrnator
  4. Output from the alternator charge post
  5. Positive post on the battery
Record the values and report back
 
So it's a 68 Barracuda with HEI ignition. It is a single field alternator and the test I tried I realize now is for the dual field alternators not single. I understand that I can briefly jump the field and the alternator output together to see if it will engage the alternator.

My voltage on the battery is 12.2 the voltage at the ignition post on regulator is battery voltage as well as the output on the alternator. This of course drops slightly when key is on.
With the car running and i test the field wire on the alternator it's at .10 volts same for the regulator.
 
So you have some sort of Chrysler built vehicle with a grounded brush alternator. So we can guess its a pre-1970.
Is this correct? Yes this is correct. 1968 Barracuda 318 HEI.
See here for what is a grounded brush alternator: Identifying Chrysler Alternators (1960-1976)


I'm going to just assume nothing at the point, so my apologies for the questions.
When the engine is running what does needle on the gage labled 'alternator' do?
does it change between idle and say fast idle? There is just an ammeter gauge and it is just below center on the discharge side.

and if you know from using your multimeter:
What does the voltage across the battery read with the engine running? 11.5
What is the voltage at the alternator output terminal (the stud) ? Same




It should always be the same, key on, key off, engine running, engine not running. Both of those wires (battery positive and alternator output) are welded together under the dash.



Not sure what you are measuring here. volts to ground? Yes
If the ignition side of the regulator is not getting power with the key on (should show same voltage as battery) then there is a bad connection between the regulator ignition terminal and the key switch. This is assuming there is a good connection to the key switch from the battery and the alternator.

The regulator is getting battery voltage.
 
???

worthless27-jpg.jpg
 
The alternator, the connections at firewall, any connections related to alternator wiring,connections at the regulator, the voltage regulator itself . Pictures always make it easier to SEE what you're working on. Just my .02
 
it it an electronic regulator or a points style regulator (triangle plug or 2 lugs?) Alt requires power to energize then it will make power, the points voltage regulator turns this power off and on (duty cycle) to regulate the 14.2 V output or whatever to the battery, and then the rest of the car through the ALT/AMP meter. The electronic regulator regulates the ground connection to do the same thing with the isolated field alt with 2 F connections. Both work with their chassis mounting for ground.
 
My voltage on the battery is 12.2 the voltage at the ignition post on regulator is battery voltage as well as the output on the alternator. This of course drops slightly when key is on.
With the car running and i test the field wire on the alternator it's at .10 volts same for the regulator.
Just to be sure.

0.10V is what you are saying when you say .10 volts right. Rather than 10v which I would expect on the field wire, whether at the VR or at the alternator field terminal

All the measurements I asked you to get should have been done with the engine running. Was that so?

And as posted earlier photos help so much it's not even funny.

Example... If you have a rebuilt alt and you bought it for a 86 barracuda, it should be a single field wire round back alternator. But the supply of round backs are small so most rebuilders just convert a square back to run as a single field wire alternator.
Now if the rebuilders goofed and left both field terminals on the square back isolated then it would not work in a single field alternator setup. (Without modifications) a photo of the back of the alternator would help to determine if the terminal was properly grounded.

You can also use an ohm meter to test both field terminals with the field wires removed one should be direct short to the case, one should be at some number of ohms ( in the 10s ohms IIRC), if both are OL (infinite resistance, or Open circuit) to the case then it is an isolated (2 field wire) alternator.

So many more tested to locate the issue
 
So it's a 68 Barracuda with HEI ignition. It is a single field alternator and the test I tried I realize now is for the dual field alternators not single. I understand that I can briefly jump the field and the alternator output together to see if it will engage the alternator.

My voltage on the battery is 12.2 the voltage at the ignition post on regulator is battery voltage as well as the output on the alternator. This of course drops slightly when key is on.
With the car running and i test the field wire on the alternator it's at .10 volts same for the regulator.
Then replace the regulator BUT BEFORE YOU DO THAT
Make CERTAIN the regulator is grounded and...........

Check the alternator field current draw.

Go to MyMopar and download a service manual. What you want to find out is whether the field has something wrong with it that is drawing too much current and burning up the regulator. This can be..........

Shorted green field wire from regulator to alternator field (this has happened!!)
Broken brush insulator allowing the insulated brush to contact the case
Shorted or partially shorted field winding allowing too much current
 
So it's a 68 Barracuda with HEI ignition.
Thank you. So as 67dart273 suspected, the 'ignition' wiring has been modified. 'Ignition circuit' in Chrysler diagrams includes power to run all essential for engine operation.

It is a single field alternator
Actually they all are. Field is explained in the first post here Identifying Chrysler Alternators (1960-1976)
test I tried I realize now is for the dual field alternators not single
Post 5 shows the functional difference between regulation of the grounded brush alternator and the isolated field alternators (with two terminals and insulated brushes) Identifying Chrysler Alternators (1960-1976)
I understand that I can briefly jump the field and the alternator output together to see if it will engage the alternator.
If its a grounded field alternator...

My voltage on the battery is 12.2 the voltage at the ignition post on regulator is battery voltage as well as the output on the alternator. This of course drops slightly when key is on.
a. Something is WRONG HERE. The ignition circuit is key switched. If there is battery voltage (12.2 V) with key off, then something is miswired.
b. Put that battery on a charger sooner than later.

With the car running and i test the field wire on the alternator it's at .10 volts same for the regulator.
Putting this together with a little less than 12.2 V with key in run, engine off, my guess is the regulator is not working. Its only a guess because at this point it seems it may not be wired correctly.
The way to check is measure the voltage at the ignition terminal, the battery and the alt. output while the engine is running. Also look at the 'alt gage' to see what its indicating.

The regulator is getting battery voltage.
???? Is it or isn't it? Under what conditions?
The regulator's ignition terminal (wire going to it) should be at system voltage when the Key is in RUN.
When is Key is OFF, it should be 0 V.
 
1968 Barracuda power and charging circuits looks this.
upload_2021-8-3_18-40-48.png


Ignition-Run powered only the ignition and the alternator.

Everything connected to the battery positive is always hot.
 
-
Back
Top