1970 Plymouth 440 Quit Charging?

[ricks70dart]

Double checking before I start troubleshooting.To check for alternator charging I can put meter on battery with motor running unplug field wire and jump field to neg side of battery to make alternator charge correct? If its charging then go to regulator not sure how to check that? Everything is stock was charging fine so don't think its a wiring problem any help appreciated!

 

[Mattax]

Double checking before I start troubleshooting.To check for alternator charging I can put meter on battery with motor running unplug field wire and jump field to neg side of battery to make alternator charge correct? If its charging then go to regulator not sure how to check that? Everything is stock was charging fine so don't think its a wiring problem any help appreciated!

No. You're mixing things together.

Terms
Battery charging: This is indicated on the ammeter in the dash. (The is gage labeled alternator). If the car is running and the ammeter needle points Discharge, then the car is running on the battery and something is wrong with the alternator.
If the needle is centered or pointing somewhat to charge, then the battery is recharging or recharged and nothing is wrong.

Alternator output: People commonly call this alternator charging, but that can get confusing when troubleshooting. If the alternator is not producing enough power, or not any power, then this is what you want to troubleshoot.

Quick troubleshooting if the ammeter has been showing discharge while running:
1. Charge battery.
2. With engine running check voltage of battery positive to ground, and then alternator output to ground. Make sure the multimeter is set to DC Volts.
It should be the same at both locations, and should be 13.9 - 14.8 V. If its less, increase to fast idle to see if that changes anything.
3. Test whether its a problem in the regulator or the alternator.
a. Disconnect the green field wire.
b. jumper that field terminal on the alternator to ground.
c. Check alternator output voltage (stud terminal to ground) and the ammeter.
^^^This test bypasses the regulator's internal control, full fielding the alternator. If the alternator is working sightly revving the engine will cause the voltage to increase. Be careful when increasing engine rpm as voltage will climb.
4. If the problem is not in the regulator, make sure the field is getting power. Check the voltage at the blue wire (back probe the connector).
If it is at system voltage, then most likely an alternator problem.

The tests may make more sense if you read through the 'how it works' here Identifying Chrysler Alternators (1960-1976)

 

[67Dart273]

Double checking before I start troubleshooting.To check for alternator charging I can put meter on battery with motor running unplug field wire and jump field to neg side of battery to make alternator charge correct? If its charging then go to regulator not sure how to check that? Everything is stock was charging fine so don't think its a wiring problem any help appreciated!

Run over to "MyMopar" and download yourself a service manual. You may have to settle for Dodge vs Plymouth.

70 is the first year of the isolated field setup, incorrectly called 'dual field.' One field terminal (blue) gets 12V from the key with ignition "in run." The regulator controls "the amount of ground" on the other terminal (green) going back to the regulator

1...Pull green wire off alternator. Connect a jumper from that alternator terminal and run engine, determine if it charges. If not, determine if power is going through the field (bad brushes, etc)

To do that, measure voltage with key "in run" at the blue wire with the jumper you used grounded. Should be close to "same as battery" voltage. In subdued lighting, you should be able to connect/ disconnect the jumper and see a small spark. Another clue is to monitor voltage at the blue going to the one field terminal, and while watching the meter, ground/ unground your jumper. If it is drawing current, the voltage will drop a small amount.

2....If the alternator charges in (1), determine if the rest of the field wiring is OK. To do that remove the BLUE field wire, and connect the jumper from there to ground. Unplug the VR and rig a jumper between the two harness connector terminals. This does the same thing as (1) except now the blue at the VR connector is supplying 12V, you are jumpering to green, and to the field, and then a jumper from the remaining field terminal to ground. Once more it should charge If so..........

3...Make absolutely certain that VR is grounded. "Work" the VR connector in/out of the VR several times to "feel" for tight and to scrub the terminals clean. Inspect the connector terminals carefully for corrosion. While running "wiggle test" the connector If it will not charge, and (1) and (2) tested good, replace the VR

If it will not charge in (1) or (2) either fix or replace the alternator

 

[67Dart273]

My all-time favorite car was my 70 440-6 which I bought about '72 from a friend while stationed at NAS Miramar, San Diego. I wish I had it back