Rectifier Test

Remove rectifier from alternator. Adjust ohmmeter to x1 scale. Place one lead on one of rectifier "BAT" blade terminals. Place other lead on each of the 3 stator terminals. See Fig 1 . Reverse leads and repeat test. Note readings in both directions.
Reading of approximately 7 ohms in one direction and no reading with leads reversed should be obtained.
Place one lead on rectifier base plate and remaining lead on each of the 3 stator terminals. This is done to test negative diodes. Reverse leads and repeat test.
Reading of approximately 7 ohms in one direction and no reading with leads reversed should be obtained. If readings are not correct, replace rectifier.

Fig 1: Testing Rectifier Assembly

Courtesy of FORD MOTOR CO.

NOTE: This is a circuit test only and does not measure capacity value.