Posted by rumplestiltskin on September 26, 2009 at 16:07:25 from (96.12.84.23):
Hi, Folks.
Please excuse the long narrative, but I want to provide enough background information to help you help me.
I bought an International 350 Utility about five months ago. It generally runs great, but the electrical system has seemed a little squirrely right from the start.
With the battery disconnected, the ammeter pegs at full charge. Same thing with the battery reconnected. After starting the tractor, the ammeter looks normal – a reasonable charge rate. (I’ll worry about the ammeter later.)
A couple of weeks ago a generator (12-volt Delco-Remy 1100 305, two brushes) bearing seized. The previous owner had the generator belt on WAY tighter than spec, so it destroyed the fan belt instead of the generator belt.
I replaced the generator bearings; the brushes and commutator looked good.
Just for fun I had a look at the voltage regulator. (The system had been converted from 12V positive ground to negative ground, and I wanted to see if I could tell if the regulator had been replaced with a proper one for that polarity.) The regulator is basically full of rust; the points are very dirty and I can’t tell for sure if one set is welded together. I never did find any indication of polarity. (I’ll worry about that later, too.)
The thing I’ll worry about first is the generator; I want to make sure it’s putting out power. I followed John T.’s troubleshooting Step 8 to motor test the generator in a bench vise. These are the results:
12V applied to ARM post, Field post grounded: Generator runs well.
Same, but Field post disconnected: Generator stops (should speed up instead).
Arm terminal - to - ground resistance per digital ohmmeter: 0 Ohms.
Field terminal - to - ground resistance per digital ohmmeter: 0 Ohms.
Voltage per analog voltmeter at Arm terminal (with reference to generator frame) at 1,725 rpm:
+26V DC with Field terminal grounded 0V DC with Field terminal not grounded
So, I suspect some sort of problem with the field.
And finally, my questions:
1 – Does my “field problem” hunch make sense?
2 – If so, what are the likely points of failure in the field coils?
3 – Should I really care, as long as the generator is producing 26 volts at 1,725 rpm? In other words, won’t a properly functioning voltage regulator knock it down to about 14 volts anyway, or does the regulator actually control the generator’s output and therefore need a properly operating field?
Thanks in advance and, again, sorry about the length.
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