Challenger 35, Challenger 45 and Challenger 55 Agricultural Tractors Electronic Systems Caterpillar

Four electrical tests will be required to properly troubleshoot electrical concerns on the machine. Each test is described in detail. Ensure all steps are reviewed and followed when testing.

• Continuity test, short to ground.

• Voltage measurement, short to 12 volts.

• Resistance test for components.

• Continuity test, open circuits.

Continuity Test, Short To Ground

1. Turn the power OFF. Turn the key start switch to the OFF position. Some procedures will require that the battery be disconnected. Other procedures will require that a fuse shoud be pulled out.

2. Disconnect the connectors at each end of the circuit in order to prevent false readings.

3. Set the meter to measure resistance or ohms. Measure circuit resistance. Use black lead to make contact with a plated metal part on the chassis. Make sure the surface of the component is not corroded. Use the red meter lead to touch the connector pins, one pin at a time, avoid contact with the case of metal connectors.

4. Determine if measured resistance falls within guidelines specified in the procedure. Three to four ohms indicates a direct short to chassis ground. It must be located and repaired. Higher resistances usually indicate circuit paths through modules. An additional connector needs to be disconnected to perform the test. More than 100K ohms indicates the circuit is free of shorts to ground.

Voltage Measurement Or Short To Positive Supply Volts

1. The key start switch is in the ON position. (The key start switch is in the OFF position for some specified procedures).

2. Disconnect the connectors at the sensor, the switch, or the potentiometer. All other connectors must be reconnected in order to perform the test.

3. Set the meter in order to measure DC volts. Use the red meter lead to touch the connector pins, one pin at a time. Avoid contact with the case of metal connectors. Use the black lead to make contact with a plated metal component on the chassis. Make sure the surface of the component is not corroded.

4. Determine if the voltage that was measured falls within the guidelines that are specified in the procedure.

Resistance Test For Components

1. Disconnect the component from the machine harness by unplugging the electrical connector of the component.

2. Set the electrical meter to measure resistance. Insert test probes into connector terminals specified in procedure. When you are checking potentiometers, measure from the wiper terminal to each of the other terminals while you are turning the shaft of the potentiometer. This will ensure that no open spots escape detection. When you are checking rocker or rotary switches, actuate the switch while measuring for opens and shorts.

3. Compare the values that were measured to the values in the procedures. Allow ± 5 percent of range tolerance for all measurements.

   Note: The following components cannot be tested by measuring the resistance because active devices are inside:

   • Engine coolant temperature sensor.

   • Aftercooler temperature sensor.

   • Transmission oil temperature sensor.

   • Engine oil pressure sensor.

   • Draft pin sensors.

   • Flasher relay module.

   • NASO converter module.

   • Gear shift switch.

   • Electronic Monitoring Center (EMC).

   • Right Hand Controls (RHC) module.

   • Chassis Control Module (CCM).

Continuity Test, Open Circuit

1. Turn the key start switch to the OFF position. (Disconnect the battery for some procedures. Remove fuses for some procedures.)

2. Disconnect the connectors at both ends of the circuit. All other connectors must be reconnected in order to perform the test.

3. Set the meter to measure resistance. Measure the resistance of the circuit. Use the red meter lead to touch the connector pins, one pin at a time. Avoid contact with the case of metal connectors. Use the black lead to make contact with the connector pin at the other end of the circuit. Avoid contact with other pins in the connector and the connector case, if it is metal.

4. Determine if the resistance that was measured falls within the guidelines that are specified in the procedure. If the resistance is no more than 3 to 4 ohms, the circuit is continuous. More resistance usually indicates dirty or corroded terminals in connectors. 100K ohms indicates an open circuit.