REGULATOR AS 3920266 - Caterpillar

Mechanical Faults
Table 1
Symptom    Repair    
Excessive overheating of one or both of the bearings     If the bearing has turned blue or the bearing grease has turned black, replace the bearing.    
The bearing is not fully locked in the bearing cage.
The end shields are incorrectly aligned.
Excessive overheating of the generator frame     Air flow is partially blocked or air is being recirculated from the generator or the engine.    
The generator is operating at a voltage that is too high.
The generator is overloaded.
Excessive vibration     Misalignment of the coupling    
The rotor is not balanced correctly.
Excessive vibration and a humming noise from the machine is present     The phases of the generator have unbalanced loads.    
The stator has a short circuit. Electrical Faults
No Voltage
Connect a 12 V battery to terminals "E+" and "E-" on the voltage regulator for 2 to 3 seconds. Connect the "+" battery terminal to the "E+" terminal on the voltage regulator and connect the "-" battery terminal to the "E-" terminal on the voltage regulator.Expected Result: The generator builds up voltage and the voltage remains correct when the battery is removed.Results:OK - The generator builds up voltage and the voltage remains correct when the battery is removed. There was a lack of residual magnetism. Reconnect the wires of the generator to the "E+" and "E-" terminals on the voltage regulator. STOP.NOT OK - The generator builds up voltage but the voltage does not reach the rated value. Check for the following problems:
The connections for the voltage reference on the voltage regulator are incorrect.
There is a faulty diode.
The armature has a short circuit.STOP.NOT OK - The generator builds up voltage but the voltage decreases when the battery is removed. Check for the following problems:
The voltage regulator is faulty.
The exciter stator has an open circuit.
The main stator has an open circuit.STOP.Low Voltage
Check the engine speed.Expected Results: The engine speed is correct.Results:OK - The engine speed is correct. Go to step 2.NOT OK - The engine speed is not correct. Increase the engine speed until the speed is correct. STOP.
Check the connections of the voltage regulator.Expected Results: The connections of the voltage regulator are incorrect.Results:OK - The connections of the voltage regulator are incorrect. Correct the connections of the voltage regulator. STOP.NOT OK - The connections of the voltage regulator are correct. Check for the following problems:
The voltage regulator is faulty.
There is a faulty diode.
The main stator has a short circuit.High Voltage
Adjust the voltage adjust potentiometer on the voltage regulator.Expected Results: The voltage can be adjusted to the rated value.Results:OK - The voltage is adjusted to the rated value. STOP.NOT OK - The adjustment is not effective. Replace the voltage regulator. STOP.The Voltage is Unstable
Adjust the stability potentiometer on the voltage regulator.Expected Results: The voltage can be stabilized by adjusting the stability potentiometer.Results:OK - The voltage is stabilized. STOP.NOT OK - The adjustment is not effective. Check for the following problems:
The engine speed is incorrect.
The connections on the voltage regulator are loose.
The voltage regulator is faulty.