STARTING MOTOR GP-AIR 2627124 - Caterpillar

Illustration 1 g00873381
Rectifier (1) Negative diode clips (2) Grounded heat sink (3) Positive diode clips (4) Insulated heat sinkFor the following tests, bend positive diode clips (3) and negative diode clips (1) away from the studs. The diode clips must not touch any part of the rectifier.Note: It is not necessary to remove the rectifier from the alternator.Positive Diode Check
Set the multimeter to the diode scale.
Connect the multimeter leads across insulated heat sink (4) and one positive diode clip (3) .
Record the multimeter reading.
Reverse the multimeter leads.
Record the multimeter reading.Expected Result: One reading is "0L" and the other reading is .4 to .9 volts.Results:OK - One reading is "0L" and the other reading is .4 to .9 volts. The diode is normal. Repeat steps 2 through 5 for the other positive diodes. If all of the positive diodes are normal, perform the Negative Diode Check.NOT OK - Both readings are "00". The diode is shorted. Replace the rectifier. STOP.NOT OK - Both readings are "0L". The diode is open. Replace the rectifier. STOP.Negative Diode Check
The multimeter remains on the diode scale.
Connect the multimeter leads across grounded heat sink (2) and one negative diode clip (1) .
Record the multimeter reading.
Reverse the multimeter leads.
Record the multimeter reading.Expected Result: One reading is "0L" and the other reading is .4 to .9 volts.Results:OK - One reading is "0L" and the other reading is .4 to .9 volts. The diode is normal. Repeat steps 2 through 5 for the other negative diodes. If all of the negative diodes are normal, the rectifier is normal. STOP.NOT OK - Both readings are "00". The diode is shorted. Replace the rectifier. STOP.NOT OK - Both readings are "0L". The diode is open. Replace the rectifier. STOP.