Testing Alternator/Regulator Allis Chalmers 190XT

Testing Alternator Output

The first thing to do, is to test the alternator to see if it’s actually charging.

1:  Disconnect the harness at the regulator after the motor has been started.
2:  Use a jumper cable/wire to connect wire 3, and Field wire.
This should be done after the motor has been started as said…………
If, after the jumper has been connected, the ammeter shows a charge…………..the alternator is good.

If the alternator is not charging, according to the ammeter on the dash panel……..you have a bad alternator…..or some bad wiring.

Testing The Wiring

1:  Motor off……..disconnect the wiring at the regulator.
2:  Use a voltmeter, and test for voltage at the harness, not the regulator.

Test The Field Wire
And Ground Wire
For Continuity

Using a multimeter, switch the selector to OHMS.
Remove the Field wire from the alternator.
Using a jumper wire……ground the Field wire to the body of the tractor.

Attach the positive lead from the multimeter to the Field wire at the regulator where it’s been disconnected, and the ground lead from the multimeter to a good ground on the body of the tractor.

You should show some resistance……….if the resistance is 0…..the wire has a break in it, and needs to be repaired.  This is called discontinuity.Note that the field connection is on the right side of the dual tab plug-in.  It may be marked “F”, or it may not.  This is the wire that needs to be removed, and grounded for the continuity test.

TEST THE ALTERNATOR GROUND WIRE IN THE SAME MANNER.  The ground wire coming from the alternator is connected to the regulator at this position.There is a connector underneath the regulator.  This has to be continuous, and it has to be grounded ON THE REGULATOR.

To test if the regulator is grounded…….simply touch the positive lead on the ohmmeter to the body of the regulator at the base, and ground the negative lead on the body of the tractor.  You should show resistance.

Testing The “Batt” Wire
On The Alternator

With key off……..the “Batt” terminal should be hot.  If not….check for continuity as outlined above.

The Results

If the alternator shows output on the dash panel, after the regulator has been taken out of the circuit, as above………..it’s good.

If, after all wiring tests have been performed, and the results are good……….you need a new regulator.

Buyer Beware

When shopping for replacement electrical parts, DO NOT SPECIFY PARTS FOR THE ALLIS CHALMERS 190XT.  Specify parts (alternator and regulator) for a 1970 Chevrolet C-10 pickup truck.  The parts will be cheaper. 


Any day above ground is a good day

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