Re: Farmall H 6 Volt Voltage Regulator - Resistor

Posted by Ed McCullough on May 25, 2006 at 19:37:04 from (209.158.19.70):

In Reply to: Farmall H 6 Volt Voltage Regulator - Resistor on F posted by Ed McCullough on May 21, 2006 at 12:19:10:

All,

Thanks for the helpful comments.

As it turns out, my problem was dirty contacts on the voltage/current regulating contacts in the regulator. Basically, the electrical continuity between the field post on the generator and ground was disrupted, even when the contacts were closed. After I cleaned the contacts and polarized the generator, normal charging function returned. This is consistent with the fact that I was able to get the generator to charge when the generator's field post was directly grounded to the frame, but not when hooked up to the "F" lug on the regulator.

I did experience a bit of frustration during this process due to a botched polarization process. On my initial attempt I did not run a temporary ground from the generator field post to ground when I briefly jumpered from "A" terminal on generator to "BAT" lug on regulator, and this did not work; I had to ground directly from "F" post to frame to sucessfully polarize. I suspect this is due to the high freqency opening and closure of the regulator current/voltage contacts which occurs during normal operation of the contacts.

Interestingly, before polarizing properly, the cutout relay contacts did not function properly either. With the engine off, the normally open contacts stayed stuck together! There was not enough electromagnetic force to draw the contacts together after they were manually pulled apart, but there was enough to hold them together if contact was made. I believe that during normal operation the direction of current flow from the battery acts to "push" the contacts apart electromagnetically to aid in a "clean" disconnect; current flow in the wrong direction would have exactly the opposite effect and pull (or stick) the contacts together. I do not fully understand this, as I do not quite "get" the whole polarization thing, but it certainly seems to enter the equation. After polarization the cutout contacts separated normally when the engine was shut off.

The generator P/N is 1101355, and the comments make sense that the power resistor on the regulator replaces the (no longer used) shunt resistor on the 4 position switch which is on the tractor to limit the field ground and thus the charging current. Sounds like a good idea to keep the resistor in place to avoid potential problems. The resistor was not the issue or defective; the incorrect assumption that the I had electrical conductivity through the contacts took me down the wrong logic path.

An excellent discussion which was very helpful in understanding the generator and regulator operation was found at http://www.simpletractors.com/service/electrics/2_pole_regulators.htm and associated links.

Again, many thanks for sharing your knowledge.

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