I have a funprojects voltage regulator on a stock 6V generator. I have had NO PROBLEMS for 5 years or so--worked perfectly. Today on a drive, my ammeter showed wild charging fluctuations at higher revs, some off the scale, over 20A charge. The fluctuations would cease at lower speed or at idle. Normal discharge with lights, horn & stop lamp. I opened the inspection band and observed markedly more sparking when goosing the throttle, again with wildly high fluctuating (up and down) readings on the meter. I have a stock large NOS ammeter. Took off the generator and inspected on bench. I sanded the armature to high copper polish & cleaned between the segments with a sharp point and blew out dust with compressed air. Noticed about three sixteenth's inch of play (in and out, pulling the gear) on the armature. No signs of loose wires or shorts in the generator or elsewhere on the car. Never any problems until now (nothing new done to the car)
After cleaning armature and between segments, the fluctuations ceased but no evidence of current limiting by the regulator. Moved 3rd brush fully counterclockwise (lowest setting) but still shows increasing charge along with increased revs until off the scale. Also swapped out to my old diode cutout which shows the same behavior, so I think the problem is with the generator, not the regulator. I am stumped.
I wonder about your ammeter.
How are all your connections between the regulator and the battery? If the starter works properly, the connections at the battery and the starter switch are probably ok, but a loose connection elsewhere could appear to the voltage regulator and generator as a dead battery and so would give you full charge. Or the voltage regulator could be worn out.
You didn't say whether you are running on magneto or battery. A coil problem could also cause a similar fluctuation if you are running on battery.
Another problem with generators is when the commutator has been turned down sometimes the brushes will not make good contact with the segments. New brushes might help for a while until they wear down and then again will not make good contact.
Ammeter good, wiring connections good clean and tight, running on both mag & battery, the behavior is the same.
What stumps me is that after swapping out to my old cutout and moving the 3rd brush fully counterclockwise (lowest setting) it still shows increasing charge along with increased revs until off the scale.
Main question: What would cause the generator to not be able to limit the current with the 3rd brush setting at minimum?
This is caused by the generator not seeing the battery. Like Norman said it is likely that you have a bad connection somewhere between the cutout and the battery.
Remember FP VR's do not tolerate poor quality battery disconnect switches well..
Model T generators do not tolerate poor quality disconnect switches well either!
No battery disconnect switch, only a 25A fuse on the yellow main wire at battery connection. I doubt the fuse is bad since lights & horn function with engine off. I will check that and all wiring/connections this weekend.
When you drive with the lights on do they get very bright and then burn out? This is also a symptom of poor connection to the battery. The generator sees it as a dead battery and the voltage goes up.
When you drive with the lights on do they get very bright and then burn out? This is also a symptom of poor connection to the battery. The generator sees it as a dead battery and the voltage goes up. This is an advantage of having 3 model T's. I can swap parts until I find out which one is causing the problem or find out which ones are not causing it!
I ran new 12ga wires on the charging circuit and checked all connection endpoints, along with confirming a good negative ground to frame connection. Now the funprojects VR functions as a simple cutout; steady 10A charge on a fully charged battery at speed. No current tapering down to 1 or 2A after initial jump on a fully charged battery as was customary for the last 8+ years.
Do these units wear out?? Mr. Regan......?
Check for short by the ammeter in the wiring someplace. I had the same symptoms in mine a while back. The culprit was a shorted wire on the dash courtesy light. When i would hit a bump it would short out on the dash metal where the insulation had deteriorated and broken off the wire core. Took the wire out, replaced it with a good 12 ga. wire and no more issues.
Didn't see this posting till tonight. I got email from Mike before I saw this posting so will work with him offline.