Generator/VR gremlins

[Sean Jackson]

Working on my ‘48 Windsor, all original setup with 6V pos. ground, generator and mechanical VR. 
Earlier today I noticed that the ammeter was suddenly showing no charge. Upon speeding up the engine, there was no response from the meter until I heard one of the points in the VR click around 1,500 RPM and I could just barely see the meter move. I went about testing things per the shop manual to see where the problem could be and started with the quick and dirty test of temporarily grounding the field terminal on the VR to see if there was any response from the ammeter. I held the jumper across the terminal and ground for only a split second, there was a spark, and the needle jumped back to a charging position.
Now, after that brief test, the needle now responds as it normally would! Revving the engine the needle climbs slowly, eventually the VR clicks and the needle jumps a little higher yet. Turning on the headlights at idle the needle swings back to discharge, racing the engine brings it back up to about a 10A charge. 
 

What did I do? I appreciate any advice from those who truly know how these devices operate. 
 

thanks, Sean

[Sniper]

This might help

 

 

[Plymouthy Adams]

you could have flashed the residual magnetism back into the unit...

[Sean Jackson]

1 hour ago, Sniper said:

This might help

 

 

The unit makes a lot more sense to me now, thanks Tech! 
I’m thinking it may just be out of adjustment. When I have more daylight I’ll pull it apart and check the gaps with a set of feelers. I haven’t got an ammeter that can handle the operating range yet. 

[Sean Jackson]

1 hour ago, Plymouthy Adams said:

you could have flashed the residual magnetism back into the unit...

I was wondering about that. I did the regular gen. polarization before by quickly zapping between the batt. and arm. terminals when I was dealing with the problem but it didn’t do anything to change the situation. Then I grounded the field temporarily and it’s all back to normal. Weird.  

[Sean Jackson]

Alright, I messed around with it a bit more today. Same problem was happening again, no charge indicated no matter the engine speed. Did the shop manual test of temporarily removing the arm. wire at the VR and striking it against a ground with engine revving to check for a spark. This would indicate the gen. is making juice but not making it past the VR. I got a spark, so the manual pointed toward an issue at the VR circuit breaker. I opened the VR up and watched the circuit breaker points as I raced the engine. They began to vibrate and move toward the closed position but did not fully close. I had my fiancée sit in the car and observe the ammeter while I revved the engine and pushed the CB points closed with my finger. Viola, a solid 10A or so charge on the dial. 
 

So, it appears that’s the issue. The VR I have is very easy to adjust the points gap for the circuit breaker. 
 

My question now is just how wide should that points gap be? I guess I can just trial and error it so that it kicks on just off of idle but I don’t want to set them so narrow that the generator becomes a motor at low engine speed. Any tips?

[chris 48 P15]

looks like two diff. sets of points on regulator for adjustment

one on circuit breaker and one each on the volt regulators

pictures are from 1946 to 1954 Plymouth service manual

 

[Merle Coggins]

I had a voltage regulator start doing that a few years ago. I finally replaced it with a new one and the problem was solved. I believe something happened to the circuit breaker coil and it got too weak to pull the points closed when needed. 

Edited June 2, 2022 by Merle Coggins