Disassembly and Assembly
Generator - CS 121 DIFDisassembly Procedure
1. Remove the generator. Refer to "Generator" in the On-Vehicle Service.
2. Mark a match line that cannot easily be removed on the end frame to make assembly easier.
3. Pry off the plastic cover to expose the stator connections.
NOTE: If the stator connections are not welded, melt the lead. Avoid excessive heating, as it can damage the diodes in the rectifier bridge.
4. Remove the stator connections from the rectifier bridge terminals by cutting the wires.
5. Remove the generator through-bolts.
IMPORTANT: The fastening torque of the drive end bearing nut is 81 N.m (60 lb-ft) and may not normally be unfastened using hand strength.
6. Remove the drive end bearing nut.
7. For vehicles with an internal fan, remove the pulley and the collars.
8. Test the rotor for an open circuit by using the ohmmeter with the drive end frame assembled. The reading should be sufficiently high, or the rotor must be replaced.
10. Test the rotor for open and short circuits. The reading should be 1.7 to 2.3 ohms, or the rotor should be replaced.
11. Remove the drive end frame from the shaft.
12. For vehicles with an internal generator fan, remove the drive end frame and the fan.
13. Remove the rotor assembly.
14. Remove the stator.
15. Test the stator for an open circuit using the ohmmeter.
16. Pry off the baffle.
17. Remove the rectifier/regulator/brush holder assembly screws.
18. Remove the brush holder assembly and the regulator, cutting the terminal between the regulator and the rectifier bridge.
IMPORTANT: It the brush can be reused, reassemble the brush to the holder with the retaining pin, after cleaning the brush with a soft, clean cloth.
19. Test the rectifier bridge by connecting the ohmmeter terminals to the bridge and the heat sink
20. Retest by connecting the ohmmeter terminals in the reverse order.
21. Replace the rectifier bridge if each reading is the same.
22. Test the remaining two diodes after the above procedure.
NOTE: Some kinds of digital ohmmeters are not suited for testing the bridge diode. In this case, consult the manufacturer regarding the test capacity.
23. Test the diodes by connecting the ohmmeter terminals to the bridge terminal and the base plate. If the reading is the same, the rectifier bridge should be replaced.
24. Remove the ring in the slip ring end frame.
Assembly Procedure
1. Install the new ring in the slip ring end frame.
2. Push the new bearing outer race into the bottom of the end frame casting.
3. Weld the brush holder terminal to the regulator terminal, if removed.
4. Fix the brush holder with the retainer pin, and weld the regulator/brush holder assembly terminal to the rectifier terminal.
5. Apply silicone grease between the bridge and the end frame for radiation purposes.
6. Fasten the screws holding the rectifier regulator/brush holder assembly to the end frame.
7. Punch the new baffle with the pin into the brush.
8. Install the stator.
NOTE: Take care to protect the diode in the rectifier bridge from excessive heat while welding.
9. Weld the connectors of the rectifier bridge.
10. Install the outside cover.
11. Position the rotor assembly shaft with the drive end frame in the slip ring end assembly until the gap between the outer race and the end frame casting is 1.9 mm (0.075 inch).
12. Install the generator through-bolts.
Tighten
Tighten the generator through-bolts to 10 N.m (89 lb-in).
13. Position the fan, the collars, and the pulley on the rotor shaft and secure with the nut.
Tighten
Tighten the generator drive end bearing nut to 81 N.m (60 lb-ft).
14. Install the generator. Refer to "Generator" in the On-Vehicle Service.