Checking Components: Delco CS130 and CS121 Alternator Rebuild Instructions, Part 5

Stator Checks

If an ohmmeter reads low or lamp lights when connected from an stator lead to bare metal on the test the delta stator for shorts or opens. Noticeable discoloration at any place on the assembly usually indicates defective stator windings.

Bridge Rectifier Check

The rectifier is the number one failed component on the CS-130 alternator. To check rectifier bridge, connect ohmmeter using low scale from bridge terminal to heat sink, then reverse connections (Figure 8). If both readings are the same. replace the rectifier bridge. Connect from other two terminals to heat sink in same manner to check other two diodes. Connect between three terminals and base plate (Figure 8) to check remaining three diodes in rectifier bridge. Notice: Some digital ohmmeters cannot be used to check diodes in rectifier bridge.

REGULATOR
The regulator cannot be checked with an ohmmeter. Use only an approved tester to test regulators of this type.

Brush Holder

If the brushes are to be reused, clean with a soft, dry, cloth. Replace the brush holder assembly if brushes are excessively worn.

Slip Ring Maintenance

It the slip rings are dirty, they may be cleaned and finished with 400 grain or finer polishing cloth. Spin the rotor. and hold the polishing cloth against the slip rings until they are clean. CAUTION: The rotor must be rotated in order that the slip rings are cleaned evenly.

Cleaning the slip rings by hand with-out spinning the rotor may result in flat spots on the slip rings, causing brush noise. Slip rings that are rough or out of round should be trued in a lathe to 002 inch maximum indicator reading. Remove only enough material to make the rings smooth and round. Finish with 400 grain or finer polishing cloth and blow away all dust.