Open Field Or Short Circuit
- Perform test before alternator disassembly. Adjust ohmmeter to lowest scale. Place ohmmeter leads on regulator "A" terminal and regulator "F" screw head. See Fig 1
. Rotate alternator pulley and note reading. Reverse ohmmeter leads and repeat test.
Courtesy of FORD MOTOR CO.
- Reading should be between 2.2-100 ohms in one direction. Fluctuation may occur while pulley is turning. Reading should fluctuate between 2.2-9 ohms with leads reversed.
- Reading with approximately 9 ohms in one direction and no reading in the other indicates open brush lead, defective brushes or loose regulator-to-brush holder attaching screws.
- Reading of less than 2.2 ohms in both directions indicates a shorted rotor or defective regulator. Reading exceeding 9 ohms in both directions indicates a defective regulator or loose "F" terminal screw.
- Place one lead on alternator rear housing with remaining lead touching regulator "F" terminal. Note reading. Reverse leads and repeat test. Reading should be infinite in one direction and approximately 9 ohms with leads reversed.
- Reading less than infinite in both directions indicates a grounded brush lead or defective regulator. Reading exceeding 9 ohms in both directions indicates defective regulator or "A" terminal connection.
Courtesy of FORD MOTOR CO.