Charging

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dancinwulf

dancinwulf

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I have replaced the alternator and voltage regulator ground the firewall and back of the voltage
regulator in seems to charge until it gets warm then stops runs just at 12 volts. Even with the electric fan running doesn't seem to charge
 
Year, make, model?

I do not understand your post. Did you replace the actual alternator and the actual VR or did you just add a ground wire?
 
I replaced both the alternator and the VR ground the coating off the VR and the
fire wall to make a good connection for the ground. I worked for a short while
and then quit charging.
 
dancinwulf said:
I replaced both the alternator and the VR ground the coating off the VR and the
fire wall to make a good connection for the ground. I worked for a short while
and then quit charging.
Click to expand...
AND YOU STILL HAVE NOT ANSWERED THE QUESTION what is it that we are working on??

This is a TWO WAY street. If you expect help here read and answer the questions. You are wasting my time. I am not getting paid for this
 
dancinwulf said:
I replaced both the alternator and the VR ground the coating off the VR and the
fire wall to make a good connection for the ground. I worked for a short while
and then quit charging.
Click to expand...
It seems to only charge when the motor is cold or when you first drive it after awhile
it stops charging
 
Not sure what ;you are asking its a 1970 plymouth duster 340 which doesn't want to charge
 
A. The battery only charges when it low. So if you are judging charging by the 'alternator' gage, everything may be correct.
After starting the needle swings over from D (Discharge) to C (Charge) until the battery is recharged. Middle position means the alternator is working and the battery's power is not needed.

B. People commonly use the word charging when they actually mean alternator output. That's not the same as actually charging the battery. The ammeter in the dashonly indicates whether the battery is discharging or charging; it does not directly indicate alternator output. We know the alternator is not providing power when the battery continues to discharge while driving. You have not provided enough context for us to know how you are using the term.

C. The only electric fan these cars came with is for blowing hot air into the passenger compartment.
In other words, your car has been modified and so that opens many possibilities.
People will power electric fans from the battery - which is a bad bad modification to a stock system.
People will replace the ammeter with a voltmeter - which can be OK.
 
1691190904007.png


The wiring scheme changes slightly over the years but the overall strategy always used the ammeter in the same manner. It only shows battery discharge and charging.

This is a typical standard wiring scheme for a '70.
1691191021471.png
 
Last edited:
12 volts is low and will discharge the battery. Check the resistance between the field terminals with the key off and voltage from each field terminal to ground with the engine running and battery voltage low.

The field terminals should have less than 10 ohms resistance to each to each other. If not, something's wrong in the alternator.

The blue field terminal should have battery voltage give or take a volt. If not, there's a wiring fault that is not powering the field coil.

The green field terminal should have 0 to 1 volts if the battery voltage has dropped too low, since the voltage regulator should turn the field coil to max current. If not, the regulator isn't regulating.
 
dancinwulf said:
Not sure what ;you are asking its a 1970 plymouth duster 340 which doesn't want to charge
Click to expand...
NOT SURE WHAT YOU ARE ASKING

IT IS IMPORTANT to know what we are working with BECAUSE THE SYSTEM CHANGED MATERIALLY in 1970

69 and previous systems had a grounded field alternator with one field terminal, and a completely different VR

70 and later have an isolated (insulated) alternator field and that VR is different from the 69 / earlier types.

You have several possibilities

1...Maybe the charge path (wiring) from the alternator to the battery is open. This is the output wire, goes through the firewall connector, through the ammeter, back out through the firewall, and to the battery +

2..Maybe something in the field circuit is open/ broken, preventing the field from energizing

3...The alternator could be defective

4...The VR could be defective OR NOT GROUNDED

====================================

A...To test the alternator, disconnect the green field wire at the alternator and connect a jumper to ground. Start engine, see if the ammeter indicates a charge as you slowly bring up RPM.

If not, determine if the output circuit is OK. Put your multimeter directly on the alternator output stud (large black wire) and repeat test. If voltage comes way up, way above 16, there is something wrong in that output circuit

If instead the voltage is still low, down near 12V, the alternator MAY be defective.


================================
B...Now check out the field wiring. If the alternator did not charge in the first test, either the alternator is bad, or the blue field wire/ field circuit is open With key in "run" and the jumper still in place, check voltage "back probe" the blue wire, still connected to the alternator field. If it reads battery voltage, or close, OK

If that voltage is present, and you had no charge, alternator is bad

If no voltage, examine the wiring. Has it been modified?

C....Check other field wiring. Rerun the first check in a different way. This time, remove the blue field wire at the alternator and ground that terminal. Remove VR connector and devise a way (small screws) to jumper across the two wires at the VR connector. REconnect the green field wire at the alternator. Again measure the green wire to ground with your multimeter. It should again show battery voltage. Repeat test, AKA run engine, see if it charges.

If after these checks, with the field wiring jumpered, the alternator does not charge, and if the output stud is still low voltage, the alternator is not charging and is defective.

If the alternator DOES charge, either the VR is bad, not grounded, or the VR connector is loose. Inspect the interior of the terminals with a flashlight for corrosion. "Work" the connector on/ off the VR several times to scrub the terminals and "feel" for tightness. RE-ground VR by scraping paint of rear and around bolt holes, and use star lock washers. VR MUST be grounded.

If alternator charged in tests, replace VR
 
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