PUMP & MTG GP-MAIN HYDRAULIC 5050526 - 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 housings 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 humming     The phases of the generator have unbalanced loads.    
The stator has a short circuit. Electrical Faults
Exciter Field Flash for No Voltage Output
Self-excited generators may lose the residual magnetism that normally exists in the exciter field and the main field. Residual magnetism is necessary to start the generation process. The magnetism can be restored by flashing the exciter field with direct current. A 6 V automotive battery can be used to supply the direct current. Note: The generator must be stopped in order to perform this procedure.
Remove the field wires for the generator "5+" and the "6-" from the voltage regulator. Connect the "+" battery terminal to the "5+" wire on the field winding for the generator and connect the "-" battery terminal to the "6-" wire on the field winding generator for 2 to 3 seconds.Expected Result: The generator has an output voltage when the generator is started. Results:OK - The generator has an output voltage after the generator is started. There was a lack of residual magnetism. STOP.NOT OK - Proceed to the Testing and Adjusting section of Service Manual, KENR8205, "Generator Set - Test "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.