DOOR GP-ACCESS 4214416 - Caterpillar

Illustration 1 g00649573
Connect a variable power supply and two multimeters to the alternator. The alternator is completely assembled for this test. Set one multimeter as a voltmeter. Set the other multimeter as an ammeter. The setup is shown in Illustration 1.
Set the variable power supply to 0 volts. Slowly raise the power supply until the ammeter indicates a current draw.
Measure the voltage. Record the result as the "Turn On" voltage.Expected Result: The voltage is approximately 27 volts.Results:OK - The voltage is approximately 27 volts. Go on to step 4.NOT OK - The voltage is not approximately 27 volts. The regulator has failed. Replace the regulator. STOP.
The regulator remains on. Measure the current. Record the result as the field current.Expected Results: M1 Series Alternators ... 3.08 to 3.15 amperes HDB Series Alternators ... 3.26 to 3.59 amperesResults:OK - The current is within tolerance. Go on to step 5.NOT OK - The current is below tolerance or the current is 0 amps. The field winding is open or the regulator is open. Refer to Testing and Adjusting, "Field Winding - Test" in order to determine if the field winding is open. If the field winding is open, replace the field winding. If the field winding is normal, the regulator is open. Replace the regulator. STOP.NOT OK - The current is above tolerance. The field winding has a short circuit. Replace the field winding. Go on to step 5.
Divide the "Turn On" voltage by the rotor field winding resistance. Refer to Specifications, "Alternator" for the rotor field winding resistance. Record the result as the field current. Compare the current that was calculated above with the current that was measured in step 4.
The power supply remains at the "Turn On" voltage. Slowly raise the voltage until the ammeter reads 0 amps. Record the result as the "Turn Off" voltage.
Subtract the "Turn On" voltage from the "Turn Off" voltage.Expected Result: The difference is 2 volts or less.Results:OK - The difference is 2 volts or less. The regulator is normal. STOP.NOT OK - The difference is greater than 2 volts. The regulator has failed. Replace the regulator. STOP.