Low voltage problem

[hotrod swinger]

1973 Dart Swinger, basically factory wiring.

Noticed low voltage while driving, a few minutes later voltmeter stays at 12.5, no charge.

Verified with multimeter.

I have battery voltage at the alternator stud.

I removed the green wire from the alternator and grounded the field connection, started the car and the alternator started charging again.

Where do I go from here? Is there a further test for the voltage regulator I can do?

 

[67Dart273]

Make certain VR is grounded. "Work" VR connector in/ out several times to 'scrub' terminals and "feel" for tightness. Remove connector check if you have power (key in run) to BOTH terminals with all other wiring connected normal.

The blue gets battery power from the key
The green is fed back power from the blue to one field---through the field--and back to the VR on the green

You can double check field wiring is OK by jumpering across VR terminals, then removing blue wire at alternator and grounding that terminal as you did the green. If it charges, wiring is likely OK

Replace VR

These do not fail often

 

[hotrod swinger]

Make certain VR is grounded.

VR is grounded.

"Work" VR connector in/ out several times to 'scrub' terminals and "feel" for tightness. Remove connector check if you have power (key in run) to BOTH terminals with all other wiring connected normal.

Done, everything checks out.

You can double check field wiring is OK by jumpering across VR terminals, then removing blue wire at alternator and grounding that terminal as you did the green. If it charges, wiring is likely OK

Did this test, alternator charges battery.

Could this actually be a failed VR? I have a spare one I guess I’ll swap it out.

 

[hotrod swinger]

I swapped in my spare voltage regulator and problem solved, imagine that.

 

[67Dart273]

!!!Amazing!!!