Cs144 (5.7L)

Scribe end frames to facilitate reassembly. Remove through-bolts and separate end frames.
Using ohmmeter, measure coil resistance between slip rings. See Fig 1. On 5.7L, coil resistance should be 1.7-2.1 ohms at 70°F (21°C). If coil resistance is not as specified, replace rotor.
Using ohmmeter, check for grounds between either slip ring and rotor pole piece. See Fig 1. Ohmmeter should indicate infinite resistance. If reading is not infinity, replace rotor.
Resistance readings will vary slightly with winding temperature changes. If generator does not supply rated output and rotor is okay, rectifier bridge, stator or regulator is faulty.
To reassemble generator, reverse disassembly procedure. Retain brushes with brush retaining pin during reassembly. See Fig 2. Remove retaining pin after tightening through-bolts.

Fig 1: Testing CS144 Generator Rotor (5.7L)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Removing CS144 Generator Brushes (5.7L)

Courtesy of GENERAL MOTORS CORP.