BOLT 4F4879 - Caterpillar

This section provides probable causes to a known problem. There may be several probable causes to each problem. Specific inspections or tests are recommended in order to help isolate the damaged component.The generator is a component of the generator set. The generator should be tested with the entire system. The voltage regulator's service manual provides tests in order to determine if the generator is the cause of a generator set malfunction.A problem must be identified and defined before the problem can be corrected. After you identify the problem, refer to Table 1.The following procedure should be used to identify the problem:
Perform visual checks in order to help identify the problem.
If previous tests were performed from the voltage regulator service manual, use the test results to help identify the problem.
Perform the "Generator Functional Test". The "Generator Functional Test" will help identify the problem. Visual Checks
A visual inspection of the generator set can detect possible causes of a malfunction. Inspect all wiring for worn insulation or missing insulation. Ensure that all wire terminal connections are tight. Also ensure that all wire terminal connections are not corroded. Discolored electrical components indicate that the item has been greatly stressed.A large percentage of electrical problems are caused by mechanical defects. Carefully inspect the total installation. Keep the mechanical defects separate from the electrical defects.Problem List
Table 1
PROBLEM PROBABLE CAUSE REFERENCE
All Phase Voltages Are Too Low or Too High. Damaged diodes "Rotating Rectifier - Test"
Damaged exciter armature (Rotor - L2) "Winding - Test"
Damaged exciter field (Stator - L1) "Winding - Test"
Damaged PM armature (L5) "Winding - Test"
Damaged varistor (CR7) "Varistor - Test"
Damaged internal exciter winding "Internal Exciter - Test"
Damaged voltage regulator "Voltage Regulator - Test"
Damaged Sensing Leads "Electrical Connections - Check"
The Phase Voltages Are Not Equally Balanced. Damaged main armature (Stator - L4) "Winding - Test"
Operating at voltages above saturation level (over 105% rated) Adjust (lower) voltage level
Damaged Sensing Transformer (On medium voltage generator only) 1) Reconnect primary transformer leads
2) If the lower phase voltage follows reconnect lead, replace transformer
Unbalanced Load External Load Issue
Table 2
Fault Action Effect Check/Cause
No voltage at no load on start-up Measure the PMG or exciter voltage input to the voltage regulator. The generator voltage builds up and the voltage is still correct when the battery is removed. Lack of residual magnetism
Connect a new battery, that is 4 to 12 volts, to terminals F1 and F2. Observe the correct polarity. Connect the battery for only 2 to 3 seconds. The generator voltage builds up but the voltage does not reach the rated value when the battery is removed. 1) Check voltage reference connector at the AVR.
2) Faulty diode
3) Armature short circuit
Disconnect the VR and run the engine at low idle speed. The generator voltage builds up but its voltage disappears when the battery is removed. 1) Faulty AVR
2) Field windings open circuit (check winding)
3) Main field winding open circuit (check the resistance)
Voltage too low Check the engine speed Correct speed 1) Check the AVR connections (possible AVR failure)
2) Short circuit