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TROUBLESHOOTING AND REPAIR |
EXCITER ROTOR VOLTAGE TEST (continued)
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PROCEDURE (continued)
9. Set the RUN/STOP switch to “STOP”
If the meter reading is normal, this test is complete.
If the voltage measures zero or very near zero, the rotor may be shorting or grounding while spinning. Perform the Exciter Rotor Resistance and Ground Test.
If voltage is higher than specified, the engine RPM may be too high, or there may be voltage intrusion from one of the higher voltage stator windings to the stator exciter winding. Perform the Engine RPM Adjustment Test, and the Exciter Stator Short
Circuit and Ground Test.
If the voltage is lower than 124, but higher than 14, the engine RPM may be too low, or there may be problems in the windings or other exciter circuit components or connections. Perform the Engine RPM Adjustment Test, and then perform the testing described below, under the heading “If the voltage measures about 2 to 4 VDC”
If the meter reading indicates battery voltage, about 12 to 14 VDC, The rotor may be opening while spinning, or the brushes may be faulty or not making proper con- tact with the slip rings while the rotor is spinning. Perform the Rotor Resistance Test, and the Brush and Slip Ring Service Procedure.
If the voltage measures about 2 to 4 VDC, the genera- tor is not
10. Check the D1 field bridge rectifier.
11.Check the wiring and terminals connecting the D1 bridge rectifier to the Exciter stator winding. See the wiring diagram.
12.Perform the Exciter Stator Short Circuit and Ground Test.
When the Stator Short Circuit and Ground Tests have been completed, reconnect the leads to the AC termi- nals of the D1 field bridge rectifier.
Be sure that there are no loads of any kind across any of the stator windings. The exciter winding should be the only stator winding connected at this time. Examine stator wiring for damage, pinched leads, chafed insulation, etc. If necessary, disconnect and insulate the stator output leads as close to the stator winding as possible. If any leads were disconnected, secure them so they cannot be damaged by moving parts. See wiring diagram.
13.
If the rotor voltage continues to read significantly lower than 124VDC, the Stator is probably defective and should be replaced.
NOTE: The field bridge rectifier may appear to func- tion normally when tested independently, but may malfunction when placed under the stress of normal operation. For this reason, it is rec- ommended that the bridge rectifier be replaced with a known good component before replac- ing the stator.
*Voltages shown in this document are for a machine operating at normal temperature. Voltage readings may be slightly higher if the machine is cold.
