PIN 9R2846 - Caterpillar

Discrete Diode Test
Check the Bridge Diodes for the 1400 Frame and 1600 Frame Generator
Illustration 1 g01327476
To perform this diode check, the diodes must be isolated. Refer to Illustration 1.
Illustration 2 g01327478
Attach a battery and a light to each diode in both directions to test the diode. Refer to Illustration 2.
Replace the diodes that illuminate the light bulb when wired in both directions.Check the Windings and Rotating Diodes by use of Separate Excitation
Ensure that the generator is disconnected from any external load and inspect the terminal box to check that the connections are fully tightened.
Stop the unit, disconnect, and isolate the CDVR wires.
Illustration 3 g01327528
Illustration 4 g01327530
There are two ways of creating an assembly with separate excitation. Assemble one of the following test circuits.Note: The voltage from a 12 V or a 24 V battery is too high regarding the required excitation voltage when running at rated engine speed. A rheostat must be used to adjust the required excitation current for the nominal voltage at no load. Refer to Illustration 3. Refer also to Illustration 4.As an alternative, a 12 V battery that is directly connected may be used if running the engine at low idle speed. Refer to "Dynamic" flashing.Both these systems should have characteristics which are compatible with the machine field excitation power. Refer to the nameplate.
Run the generator at the recommended speed that is used during normal operations.
Gradually increase the exciter field current by adjusting the rheostat and measure the output voltages on "L1- L2 - L3". Checking the excitation voltage and current at no load and on load. Refer to the machine nameplate or ask for the factory test report.
When the output voltage is at rated value and is balanced within 1% for the rated excitation level, the machine is in working order. The fault therefore comes from the CDVR or associated wiring (that is sensing or auxiliary windings).Full Wave Rectifier and Rectifier/Varistor Rotating Heat Sink Assembly
Refer to the "Varistor - Test" section of this document for information about testing procedures.1800 Generators Only
The full wave rectifier module including internal varistor and the external varistor module should be inspected and should be tested according to the following guidelines:All leads, terminals, and connections should be inspected for damage and correct torque.All test measurements should be documented to establish trending data.Rectifier Diode Test
The following procedure tests each of the six diodes within the rectifier diode module. If any meter reading does not fall within the given ranges, replace the heat sink assembly. Refer to the "Removal/Installation" instructions.
High voltage may be present. The power source must be disconnected before working on the equipment. Failure to disconnect the power source could result in injury or death. Verify that the equipment is not energized before performing any maintenance. This work must be performed by trained personnel with correct tools and procedures. Bodily contact with electrical potential will cause personal injury or death.
Remove all leads from the rectifier diode module.
Set the digital multimeter to the diode range.
Place the black test lead of the multimeter on the