C27 and C32 Engines for Caterpillar Built Machines Caterpillar

Cooling Fan Reversing - Test

Usage:

990K A9P

Use this procedure to troubleshoot any suspect faults with the circuit for the engine fan reversing solenoid.

Show/hide table




Illustration 1	g02309533
Location of the manual purge switch for the cooling fan reversing solenoid (1) Manual purge switch

Show/hide table




Illustration 2	g02340736
Location of the cooling fan reversing solenoid (2) Control Manifold Gp (3) Cooling fan reversing solenoid

The purpose of a reversing fan is to clean debris from the radiator. By temporarily reversing the direction of the air flow through the radiator fins, debris is purged 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 rotation of the fan. The ECM will use a preset time interval to cycle the fan reversing solenoid.

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

Show/hide table




Illustration 3	g02309293
Schematic for the cooling fan reversing solenoid and manual purge switch

Show/hide table




Illustration 4	g02310116
Location of the ECM connectors (4) J1/P1 ECM connectors

Show/hide table




Illustration 5	g02339339
Terminal locations at the J1/P1 ECM connectors (P1-5) Return (P1-12) Reversing solenoid (P1-18) Return (P1-46) Manual purge switch

Show/hide table




Illustration 6	g01250541
Terminal locations at the manual purge switch (Terminal 2) Return (Terminal 3) Signal

Show/hide table




Illustration 7	g01155187
Terminal locations at the cooling fan reversing solenoid (Terminal 1) Solenoid signal (Terminal 2) Return

Show/hide table

Table 1
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the keyswitch to the OFF position. B. Thoroughly inspect the connectors. Also, thoroughly inspect all of the other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information. C. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code. D. Check the harness for abrasions and pinch points.	Electrical Connectors and Wiring	Result: The harness and wiring are OK. Proceed to Test Step 2. Result: There is a problem with the harness and/or wiring. Repair:Repair or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. If the problem is not resolved, proceed to Test Step 2.
2. Check the Resistance of the Solenoid Coil A. Turn the keyswitch to the OFF position. B. Disconnect the reversing solenoid for the variable pitch fan. C. Measure the resistance between 1 (solenoid) and 2 (Return). The correct resistance of the solenoid coil at 25° C (77° F) is 32 ± 1.6 Ohms.	32 ± 1.6 Ohms	Result: The resistance of the coil is within specifications. The coil is OK. Proceed to Test Step 3. Result: The resistance is not within specifications. Repair: There is a problem with the coil. Install a new cooling fan reversing solenoid. If the problem is not resolved, proceed to Test Step 3.
3. Use Cat^® Electronic Technician (ET) to Check the Status of the Manual Purge Switch A. Connect Cat ET to the service tool connector. B. Turn the keyswitch to the ON position. C. Observe the status for Engine Fan Reverse Switch Position on Cat ET while you operate the switch. D. Turn the keyswitch to the OFF position.	Status of the Switch	Result: The status shows the expected result. The manual purge switch is working properly. Proceed to Test Step 5. Result: The status does not show the expected result. The ECM does not recognize the input from the manual purge switch. Proceed to Test Step 4. If the problem is not resolved, proceed to Test Step 4.
4. Check the Manual Purge Switch A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the manual purge switch. C. Measure the continuity between P1-46 (manual purge switch) and P1-5 (return) with the manual purge switch in the released position. D. Measure the continuity between P1-46 (manual purge switch) and P1-5 (return) with the manual purge switch in the depressed position.	Continuity	Result: There is no continuity when the switch is in the released position. There is continuity when the switch is in the depressed position. Proceed to Test Step 5. Results: The continuity of the circuit is not acceptable. There is a problem with the manual purge switch. Repair: Replace the manual purge switch with a new switch. If the problem is not resolved, proceed to Test Step 5.
5. Check for a Short in the Harness for the Cooling Fan Reversing Solenoid A. Disconnect the J1/P1 ECM connector. B. Measure the resistance between P1-46 (manual purge switch) and chassis ground. C. Measure the resistance between P1-12 (reversing solenoid) and chassis ground. D. Measure the resistance between P1-46 (manual purge switch) and P1-5 (return). E. Measure the resistance between P1-12 (reversing solenoid) and P1-18 (return). F. Measure the resistance between P1-46 (manual purge switch) and P1-12 (reversing solenoid).	Resistance	Result: The resistance is acceptable. There are no shorts in the harness. Proceed to Test Step 6. Result: The resistance is not acceptable. There is a short between the ECM and the reversing solenoid and/or the manual purge switch. Repair: Repair the circuit. If the problem is not resolved, proceed to Test Step 6.
Troubleshooting Test Steps	Values	Results
6. Check for an Open in the Harness for the Cooling Fan Reversing Solenoid A. Remove the electrical power from the ECM. Disconnect the J1/P1 ECM connector. B. Fabricate a jumper wire that is long enough to create a test circuit across the ECM connector. Crimp pin connectors to each end of the jumper wire. C. Install the jumper wire between terminals P1-46 (manual purge switch) and P1-5 (return). D. Disconnect the reversing solenoid connector. E. Disconnect the connector from the manual purge switch. F. While the switch is activated, measure the resistance between P1-46 (manual purge switch) and P1-5 (return). Record this measurement. G. Use a suitable piece of wire to short P1-12 (reversing solenoid) and P1-18 (return). H. Measure the resistance between P1-12 (reversing solenoid) and P1-18 (return). I. Remove all shorts and reconnect all connectors.	Continuity	Result: The circuit is continuous. The wiring harness for the cooling fan reversing is operating correctly. Repair: Verify your results. There appears to be a problem with the ECM. Before you consider replacing the ECM, consult the Dealer Solutions Network (DSN) for assistance. Verify that the repair eliminated the problem. Result: The circuit is not continuous. There is an open circuit in the harness between the ECM and the solenoid and/or the switch. Repair: Repair the harness. Verify that the repair eliminates the problem.