System Operation Description:
The bypass solenoid for the engine cooling fan is used in areas with very cold ambient temperatures. Under normal operating circumstances, the main cooling fan never turns off. The main cooling fan continues to operate at a minimum speed regardless of need. When the bypass solenoid for the engine cooling fan is activated, hydraulic flow to the fan motor will be bypassed. The result is no fan speed or very slow fan speeds.
The following conditions must be met in order for the bypass solenoid for the engine cooling fan to activate.
- The temperature of the hydraulic oil must be above 21 °C (70 °F).
- The aftercooler temperature must be less than 72 °C (162 °F).
- The jacket water coolant temperature must be below 88 °C (190 °F).
- The fan return filter must be filtering hydraulic oil.
- The engine speed must be between 500 rpm and 1500 rpm.
Note: If the fan's return filter is not filtering hydraulic oil, the bypass solenoid for the engine cooling fan will be disabled.
Note: The option must be configured with the AVSpare Electronic Technician (ET) in order to enable the option.
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| Illustration 1 | g00912800 |
Test Step 1. Check for Connector Damage.
- Turn the keyswitch to the OFF position.
- Turn the circuit breaker for the engine to the OFF position.
- Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
- Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).
- Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).
- Check the harness and the wiring for abrasion and pinch points.
Expected Result:
The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.
Results:
- OK - The connectors and wiring are okay. Proceed to test step 2.
- Not OK -
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
Stop.
Test Step 2. Check for an Internal Short or for an Open at the Bypass Solenoid for the Engine Cooling Fan.
- Disconnect the connector J162/P162 for the bypass solenoid for the engine cooling fan.
- Measure the resistance between J162-1 and J162-2.
Expected Result:
The resistance should be between 24 and 53 Ohms.
Results:
- OK - The resistance is between 24 and 53 Ohms. Proceed to test step 3.
- Not OK - The resistance is less than 24 Ohms or more than 53 Ohms. The solenoid is internally shorted or open.
Repair: Replace the solenoid.
Stop.
Test Step 3. Check for a Short Circuit in the Harness.
- Disconnect the ECM connector J2/P2.
- Measure the resistance between P162-1 and P162-2.
- Measure the resistance between P162-1 and the chassis ground.
- Measure the resistance between P162-2 and the chassis ground.
Expected Result:
The resistance should be greater than 20,000 Ohms for each measurement.
Results:
- OK - The resistance is greater than 20,000 Ohms for each measurement. The wires are not shorted to ground. Proceed to test step 4.
- Not OK - The resistance is less than 20,000 Ohms for a measurement.
Repair: The wire and/or connectors is shorted to ground or to each other. Repair the wire or replace the wire.
Stop.
Test Step 4. Check for an Open Circuit in the Harness.
- Measure the resistance between pins P162-1 and P2-29.
- Measure the resistance between pins P162-2 and P2-35.
Expected Result:
The resistance should measure less than 10 Ohms.
Results:
- OK - The resistance measures less than 10 Ohms.
Repair: There may be an intermittent problem in the harness. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".
Stop.
- Not OK - The resistance measures more than 10 Ohms.
Repair: The wire and/or connectors has excessive resistance. Repair the wire or replace the wire.
Stop.