Alternator over charging?

Geo-TH,In

Well-known Member

I bought the 3 wire alternator on Jubilee from Auto Zone, lifetime warranty. Planning on taking it back to be tested. Been leveling white rock with tractor and noticed ammeter at 30 amps while engine is 900 rpms. That's not normal.

How likely is it that the white rock dust could be causing the built in voltage regulator to overcharge? Never had this happen before.
 
With 3 wire Delco alternator, #1 edge pin should connect back to switched side of ignition switch with isolating diode, lamp, or resistor in the line to prevent engine from continuing to run when switch is turned off.

#2 pin connects to battery source. On a tractor this is often looped down to alternator output.

Check to be sure connections are good and pin connections are not reversed

Be sure battery is in good condition and cables are clean and tight on both ends
 
Simple tests will place the source of your problem. When running at the above rpm, what is the voltage across the battery. If it is 14 to 14.6 the charging system is OK. If about 15 or above, the regulator is not too well, or the sense wire on terminal#2 is not connected. If lower than 14, the battery may be on its way out on one cell. Another possibility is an amp meter that is reading high. Put a known good amp meter in series with the existing meter, or replace it, to get a second opinion. (be careful to attach the new meter, so the circuit is not allowed to be open when testing.
I have seen alternators that were caked in limestone dust from gravel road use that wore out brushes and bearings, but remained electrically sound. Jim
 
Ammeter needs switched out with a volt meter. And many tractors will overcharge with an alt on them and boil a battery. They just put out too much for a system that requires very little. Using a sealed auto battery will help absorb some of the extra voltage.
 
I respectfully disagree. An alternator is far more reliable than a generator, or we would still using generators in everything. They have way fewer wear parts with 5 to 10% of the output going to input. They are self limiting in amps by design. They output far cleaner DC wave form than a generator. They have electronic (reliable) voltage control. They can go bad, but far more batteries go bad and boil because of a shorted cell, than bad voltage regulators. People wanting reliable tractors change them to alternators for the above reasons. Jim
 
The dust is not the problem.

An alternator caked with dust or grass will overheat, but not overcharge.

Check the voltage across the battery. If 15+ volts, the regulator is bad or the voltage sensor wire is disconnected from the #2 terminal.

If voltage is good, but still charging at a high rate (whining, heating up), the battery could be shorted internally.

Approach with caution!
 
I'll test battery with conductivity tester. My substitute battery before I take alternator to Auto Zone.
May use compressed air and blow dirt of alternator.
 
Like everyone else said, George: You can't assume the battery is being overcharged without first checking the voltage. And that's doubly true when a generator-to-alternator conversion is involved.

I believe the 10SI has a test feature that bypasses the regulator; you stick a screwdriver in a hole in the back of the alternator and short the metal tab inside the hole to ground. If you had anything conductive packed into that hole, it could cause the regulator to be bypassed. That's the first place I'd look.
 
(quoted from post at 10:13:54 10/06/19) Like everyone else said, George: You can't assume the battery is being overcharged without first checking the voltage. And that's doubly true when a generator-to-alternator conversion is involved.

I believe the 10SI has a test feature that bypasses the regulator; you stick a screwdriver in a hole in the back of the alternator and short the metal tab inside the hole to ground. If you had anything conductive packed into that hole, it could cause the regulator to be bypassed. That's the first place I'd look.

"If you had anything conductive packed into that hole, it could cause the regulator to be bypassed"

NICE theory, but nearly impossible in reality, IMHO.
 
Failure of voltage regulators upscale is very rare.

I would measure voltages, as suggested, and look for a loose sense wire.
 

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