C9.3 Tier 4 Interim Engines Cooling Fan Reversing - Test Caterpillar

System Operation Description:

Use this procedure to troubleshoot any suspect problems with the engine fan reverse switch or the fan reversing solenoid.

Use this procedure if either of the diagnostic codes listed in Table 1 is active or logged.

The purpose of a reversing fan is to clean debris from the radiator. Temporarily reverse the direction of the air flow through the radiator fins in order to purge debris from the radiator fins. For some applications, the reversing fan is used to heat the engine compartment during cold-weather operation.

In the automatic mode, the fan reversing solenoid is controlled by the Electronic Control Module (ECM). The ECM will automatically reverse the direction of the fan rotation. The ECM will use a preset time interval to cycle the fan reversing solenoid.

The operator can manually reverse the fan rotation by pressing the engine fan reverse switch. While the momentary switch is depressed, the direction of the fan rotation will reverse. Once the switch is allowed to reset, the fan returns to normal operation and control of the fan will return to the automatic operation.

Illustration 1	g02904976
Schematic for the fan reversing solenoid

Illustration 2	g02167868

Test Step 1. Verify Operation of the Engine Fan Reverse Switch

1. Connect the AVSpare Electronic Technician (ET) to the service tool connector.

2. Turn the battery disconnect switch to the ON position.

3. Turn the keyswitch to the ON position.

4. Check the status of the engine fan reverse switch, on Cat ET while you operate the switch.

5. Turn the keyswitch to the OFF position.

Results:

• The status changes accordingly with the switch position. - Proceed to Test Step 2.

• The status does not change with the switch position. - Proceed to Test Step 5.

Test Step 2. Check for Active Diagnostic Codes

1. Turn the keyswitch to the ON position.

2. Use Cat ET to monitor the active diagnostic code screen. Check and record any active diagnostic codes.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

3. Determine if the problem is related to an open circuit diagnostic code -5 or a short circuit diagnostic code -6.

4. Turn the keyswitch to the OFF position.

Results:

• No diagnostic codes are active. -

  Repair: The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent problems.

  STOP

• An open circuit diagnostic code -5 is active at this time. - Proceed to Test Step 4.

• A short circuit diagnostic code -6 is active at this time. - Proceed to Test Step 3.

Test Step 3. Create an Open Circuit at the Connector for the Fan Reversing Solenoid

1. Disconnect the harness connectors for the fan reversing solenoid.

2. Turn the keyswitch to the ON position.

3. Access the "Active Diagnostic Code" screen on Cat ET. Check for an active open circuit diagnostic code -5 for the fan reversing solenoid.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

4. Turn the keyswitch to the OFF position.

Results:

• An open circuit diagnostic code -5 became active after disconnecting the connector. -

  Repair: Temporarily connect a new fan reversing solenoid to the harness, but do not install the new fan reversing solenoid. Verify that there are no active diagnostic codes for the solenoid. If there are no active diagnostic codes for the solenoid, permanently install the new solenoid. Clear any logged diagnostic codes.

  STOP

• The short circuit diagnostic code -6 remained active after disconnecting the connector. -

  Repair: The short circuit is in the harness between the solenoid connector and the ECM. There may be a problem with the ECM. Refer to Troubleshooting, "ECM - Replace" before replacing the ECM.

  STOP

Test Step 4. Create a Short at the Connector for the Fan Reversing Solenoid

1. Disconnect the harness connectors at the fan reversing solenoid.

2. Fabricate a jumper wire that is long enough to create a short circuit across the terminals of the solenoid connector.

3. Install the jumper wire to the terminals on the harness side of the solenoid connector.

4. Turn the keyswitch to the ON position.

5. Monitor the "Active Diagnostic Codes" screen on Cat ET before installing the jumper wire and after installing the jumper wire.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

6. Remove the jumper wire.

7. Turn the keyswitch to the OFF position.

Results:

• The short circuit diagnostic code is active while the jumper wire is installed. -

  Repair: The engine harness and the ECM are OK. Temporarily connect a new fan reversing solenoid to the harness, but do not install the solenoid. Verify that there are no active diagnostic codes for the new solenoid. If there are no active diagnostic codes for the solenoid, permanently install the new solenoid. Clear any logged diagnostic codes.

  STOP

• The open circuit diagnostic code -5 remains active while the jumper wire is installed at the solenoid connector. -

  Repair: There is an open circuit in the harness between the ECM and the connector for the fan reversing solenoid. There may be a problem with the ECM. Refer to Troubleshooting, "ECM - Replace" before replacing the ECM.

  STOP

Test Step 5. Short the Harness at the Engine Fan Reverse Switch

1. Fabricate a jumper wire that can be used to short circuit two terminals at the harness connector for the engine fan reverse switch.

2. Use the jumper wire to short circuit terminals 2 and 3 together on the harness side of the connector for switch.

3. Turn the keyswitch to the ON position.

4. Check the status of the engine fan reverse switch-on Cat ET.

   Note: Wait at least 30 seconds for activation of the parameter.

   The correct status for the switch is "On".

5. Remove the jumper wire from the connector and check the status of the engine fan reverse switch-on Cat ET.

   Note: Wait at least 30 seconds for the activation of the parameter.

   Note: The correct status for the switch is "Off".

6. Turn the keyswitch to the OFF position.

7. Remove the wire jumper wire. Restore the wiring to the original configuration.

Results:

• OK - The status changes accordingly.

  Repair: There is a problem with the switch. Replace the switch. Verify that the repair eliminates the problem.

  STOP

• Not OK - The status does not change properly.

  Repair: There is a problem in the wiring between the switch and the ECM or between the switch and engine ground. Repair the circuit. Verify that the repair eliminates the problem.

  STOP