CYLINDER & SEAL GP-TILT 2445584 - Caterpillar

TYPE="LEVEL" DEPTH="1" @@@-->Testing A Brushless Exciter Rotating Rectifier With An Ohmmeter
Table 1
Tools Needed
Part Number Part Name Quantity
6V-7070 Digital Multimeter 1
9U-7330 Multimeter 1
146-4080 Digital Multimeter (RS-232) 1
7X-1710 Multimeter Probe Group 1
Illustration 1 g00555106 If the failure of a rectifier is suspected, use the following procedure.
Remove the cover from the exciter.
Remove the nut that secures the rectifier to the heat sink.
Remove the diode lead.
Lift the rectifier from the heat sink.
Refer to Illustration 1. Connect the ohmmeter's leads across the rectifier. Note the meter reading.
Reverse the ohmmeter leads. Note the meter reading. The ohmmeter should indicate a low resistance when the ohmmeter leads are across the rectifier in one direction. The ohmmeter should indicate a high resistance when the leads are reversed.If the ohmmeter indicates a low resistance in both directions, the rectifier is shorted. A high resistance in both directions indicates an open rectifier.Replace any faulty rectifiers with rectifiers that have comparable operating characteristics. Include the following information when a rectifier is being ordered for replacement:
Part Number of the rectifier
Model number of the exciter
Type of the exciter
Serial number of the generatorRectifier Block Test
Illustration 2 g00775020
Rectifier Block
(1) "AC1" terminal
(2) "AC2" terminal
(3) "AC3" terminal
(4) Negative terminal
(5) Positive terminal Perform the following steps in order to test the rectifier block. When possible, use the diode test scale. If there is no diode test scale, use the resistance scale.
Touch the red ohmmeter lead to the rectifier terminal that is marked "+".
Touch the black ohmmeter lead to the rectifier terminals that have the following labels: "AC1", "AC2" and "AC3". The meter should indicate an open circuit or high resistance for each rectifier terminal. If the meter does not indicate an open circuit or high resistance, the rectifier is bad. Replace the rectifier.
Touch the black ohmmeter lead to the rectifier terminal that is marked "+".
Touch the red ohmmeter lead to the rectifier terminals that have the following labels: "AC1", "AC2" and "AC3". The meter should indicate a good diode or low resistance. If the meter does not indicate a good diode or low resistance, the rectifier is bad. Replace the rectifier.
Touch the black ohmmeter lead to the rectifier terminal that is marked "−".
Touch the red ohmmeter lead to the rectifier terminals that have the following labels: "AC1", "AC2" and "AC3". The meter should indicate an open circuit or high resistance for each rectifier terminal. If the meter does not indicate an open circuit or high resistance, the rectifier is bad. Replace the rectifier.
Touch the red ohmmeter lead to the rectifier terminal that is marked "−".
Touch the black ohmmeter lead to the rectifier terminals that have the following labels: "AC1", "AC2" and "AC3". The meter should indicate a good diode or low resistance. If the meter does not indicate a good diode or low resistance, the rectifier is bad. Replace the rectifier. Replace any faulty rectifiers with rectifiers that have comparable operating characteristics. Include the following information when a rectifier is being ordered for replacement:
Part Number of the rectifier
Model number of the exciter
Type of the exciter
Serial number of the generator