SWITCH AS 3958429 - Caterpillar

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.
Table 1
Diagnostic Trouble Codes
CDL Code Code Description Comments
485-5 Engine Fan Reversing Solenoid : Current Below Normal There is an open circuit in the wiring.
Or:
There is an open circuit inside the coil for the fan.
485-6 Engine Fan Reversing Solenoid : Current Above Normal This code is caused by a short circuit in the wiring between the P2 connector and the coils for the fan.
Follow the troubleshooting procedure in order to identify the root cause of the problem. 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 g02167868Test Step 1. Verify Operation of the Engine Fan Reverse Switch
Connect the Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the battery disconnect switch to the ON position.
Turn the keyswitch to the ON position.
Check the status of the engine fan reverse switch, on Cat ET while you operate the switch.
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
Turn the keyswitch to the ON position.
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.
Determine if the problem is related to an open circuit diagnostic code -5 or a short circuit diagnostic code -6.
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