GOVERNOR AND FUEL INJECTION PUMP GROUP 7N3440 - Caterpillar

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Table 1
Common Troubleshooting Procedures (1) (2)    
Problem    Troubleshooting Procedure    
Reverse Power Shutdown     Check CT polarity.
Check connections to the digital voltage regulator terminals 5 and 6.    
No Voltage
(50 ACV or Less)     Check for the fault codes. Correct the fault codes.
Determine if DC voltage is properly connected ("B+"/"B-").
Check for loose sensing or PM wires.
Check for blown PM fuses.
Determine if underfrequency setpoint (parameter :10) is too high.
Temporarily disconnect battery from the digital voltage regulator. Then, connect battery to the regulator. Restart the regulator.
Check terminal 42. Battery voltage (24 VDC) should not be present. (Excitation disable circuit)
Check rotating diodes on the generator.    
Low Voltage
(Residual to Less Than Rated Output Voltage)     Check for the fault codes. Correct the fault codes.
Determine if generator output voltage setpoint (parameter :01) is set too low.
Determine if droop setpoint (parameter :30) is set to zero. Droop setpoint should be 0.
Check parameter :03 for correct generator type.
Determine if parameter :06 is less than the expected generator operating frequency.
Check parameter :02 for the correct PT ratio. Check that parameter :02 is not doubled.
Check that one PM fuse is not blown.
Check rotating diodes on the generator.    
High Voltage
(Voltage Higher Than Range Allows)     Check for the fault codes. Correct the fault codes.
Check parameter :02 for the correct PT ratio. Check that parameter :02 is not too low.
Check that parameter :15 (IR Compensation) is set to zero.
Determine if the generator output voltage setpoint (parameter :01) is set too high.
Determine if the minimum voltage setpoint (parameter :09) is set too high.    
Unstable Voltage
(Voltage Fluctuation Greater Than 0.25%)     Check for the fault codes. Correct the fault codes.
Remove the remote voltage adjust rheostat.
Disconnect droop current transformer.
Check for loose wiring.
Check rotating diodes on the generator.    
Initial Voltage Overshoot     Check parameter :03 for correct generator type.    
( 1 ) A regulator may fail to perform correctly if it is not properly connected. A regulator may also fail if there is a failure of downstream equipment, such as diodes.
( 2 ) It is possible to get an unexplained reverse VAR fault if the CT is connected backward. Check the CT connection if this fault occurs.This section provides troubleshooting procedures for generator voltage problems that are related to the digital voltage regulator.Note: Before starting to troubleshoot, check the part number to determine if the digital voltage regulator being used is proper for the application. The part number label on the digital voltage regulator indicates the sensing voltage range and whether or not the regulator is the optional KVAR/PF model. Refer to the following chart.
Table 2
Digital Voltage Regulator Application Chart    
Regulator Version    Voltage Range    Early Part Number    Former Part Number    Current Part Number    
Basic     79 to 124 Volt
3 phase sensing     116-7480     130-3471     155-3831    
Basic     125 to 249 Volt 3 phase sensing     116-7481     130-3472     155-3832    
Basic     250