Regulator cut in UPDATE

How many contacts in the regulator?
One is the cutout and ought to be closest to the B and A terminals on the regulator and have the biggest contacts. The others are voltage regulator and current regulator if three coils and since the control the field current which is smaller than the armature current their contacts are usually smaller.

The generated voltage being greater than the battery voltage is what causes the cutout to close, so if it only got to 13.2 volts its not generating well and that may be why the cutout is not closing. It ought to get to 14.2 in the perfect regulator. Could be the brushes are worn down or the commutator dirty or both.

Gerald J.

The voltage regulator should be vibrating if its regulating. If its not vibrating its giving the field coil all it can because its not getting enough voltage. The spring tension is increased to increase the voltage setting.

Its possible that there are three windings on that magnet, one for voltage, one for lamp load to raise the voltage a bit to account for the lamp load, and a third to sample the armature current and back off on the voltage when it gets too high.

If the regulator only regulates charging, like many, the loads take current away from battery charging. When the engine is idling that can mean more current taken from the battery. Often a generator doesn't charge at engine idle, and so the loads are supplied by the battery. Worse at a slightly fast idle I noticed my '64 beetle with lab quality volt and amp meters, that the car would draw more current from the battery than it did at slow idle because it took several amps reverse current to cause the cutout to open. When I put a 12 volt engine in a 6 volt beetle, rather than change all the loads, I built a solid state regulator with a silicon diode for the cutout and eliminated that low engine speed reverse current. Battery life was noticeably better with the solid state regulator.

If the generator brushes are sparking, they probably are worn to the point that the springs aren't pushing them against the commutator and the commutator is dirty and getting more deposits from the arcing. Sounds like it needs the attention of a good automotive electric shop that remembers how to turn commutators and fit brushes.

I have cleaned up commutators with a commercial stick made for the purpose, some soft abrasive, but that won't fix short brushes.

Gerald J.

With a voltage regulator, there will be only two brushes. The third brush was used as a current limiter that allowed the same generator to charge 6 or 8 volt batteries but also allowed overcharge that had to be counteracted by turning on headlights in the day time to absorb the current the battery didn't need. Battery life is increased with a voltage regulator.

Gerald J.

Thanks Coke, that's always a help.

I have to keep this style generator since it's a diesel the power steering drives off the rear of the gen.

A old trick is to take a pencil eraser (preferably one for ink) and just run it on the commutator of the generator . It cleans them up nice and can be done while running, and solves many problems. 

The optimum charging voltage is 14.2 volts. 13.5 is low for getting a full charge in the battery. If you have the voltage too high the battery current won't taper to zero. The SAE tolerance for that type of regulator was 13 to 15 volts being acceptable. I have a MF-135 and it was not charging well, though it had a new regulator when I got it about 1989. I adjusted the voltage and ever since it has charged better and still did last winter the last time I ran it.

Gerald J.