3126B Engine for Caterpillar Built Machines Engine Fan Control Solenoid Circuit - Test Caterpillar


Engine Fan Control Solenoid Circuit - Test
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3126B Engine for Caterpillar Built Machines [SENR9647]
ELECTRICAL AND STARTING SYSTEM
SOLENOID GP
3126B Engine for Caterpillar Built Machines Engine Fan Control Solenoid Circuit - Test

System Operation Description:

The ECM controls the speed of the fan by controlling the current to the fan control solenoid. The fan control solenoid controls the displacement of the hydraulic pump that supplies pressurized oil to the fan motor. The fan control solenoid is controlled by a signal between 0.65 and 1.8 Amp. The fan pump defaults to maximum pressure and a diagnostic code is generated if no signal is sent to the solenoid.




Illustration 1g00813712

Schematic

Test Step 1. Inspect Electrical Connectors and Wiring

  1. Turn the keyswitch to the OFF/RESET position.

  1. Thoroughly inspect the J1/P1 ECM connector and all other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

Expected Result:

All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points. All connections and grounds should be tight and free of corrosion.

Results:

  • OK - Proceed to Test Step 2.

  • Not OK -

    Repair: Repair the circuit.Verify that the repair eliminates the problem.

    STOP

Test Step 2. Check the Resistance through the Solenoid

  1. Disconnect the J508/P508 fan control solenoid connector.

  1. Measure the resistance of the sensor between J508:1 (Fan Control Solenoid) and J508:2 (Solenoid Return).

Expected Result:

Resistance should be between 4.5 and 5.5 Ohms.

Results:

  • OK - Proceed to Test Step 4.

  • Not OK - There may be a problem with the fan control solenoid. Proceed to Test Step 3.

Test Step 3. Temporarily Install a New Fan Control Solenoid

  1. Remove the fan control solenoid.

  1. Temporarily install a new fan control solenoid.

  1. Start the engine. Ensure that the keyswitch is in the ON position.

  1. Compare the status for "Fan Pump Pressure" to the status for "Desired Fan Pump Pressure" on ET.

  1. Turn the keyswitch to the OFF/RESET position.

Expected Result:

The status for "Fan Pump Pressure" should closely correlate with the status for "Desired Fan Pump Pressure".

Results:

  • OK - The fan control solenoid was faulty.

    Repair: Permanently install the new fan control solenoid.Verify that the repair eliminates the problem.

    STOP

  • Not OK - There may be a problem with the harness. Proceed to Test Step 4.

Test Step 4. Check for Shorts in the Harness




Illustration 2g00815132

ECM connector P1

  1. Disconnect the J1/P1 ECM connector and the J508/P508 fan control solenoid connector.

  1. Measure the resistance between P1:43 (Fan Control Solenoid) and chassis ground.

  1. Measure the resistance between P1:51 (Solenoid Return) and chassis ground.

  1. Measure the resistance between P1:43 (Fan Control Solenoid) and P1:51 (Solenoid Return).

Expected Result:

The resistance for each measurement should be greater than 20,000 Ohms.

Results:

  • OK - Proceed to Test Step 5.

  • Not OK - There is a short between the ECM and the fan control solenoid.

    Repair: Repair the circuit.

    STOP

Test Step 5. Check for Open Circuits in the Harness




Illustration 3g00815132

ECM connector P1

  1. Ensure that the keyswitch is in the OFF/RESET position and that the J1/P1 ECM connector is disconnected.

  1. Use a suitable piece of wire to short P1:43 (Fan Control Solenoid) and P1:51 (Solenoid Return).

  1. Disconnect the J508/P508 fan ontrol solenoid connector.

  1. Measure the resistance between P508:1 (Fan Control Solenoid) and P508:2 (Solenoid Return).

Expected Result:

The resistance should be less than 10 Ohms.

Results:

  • OK - Proceed to Test Step 6.

  • Not OK - There is an open circuit in the wiring harness between the fan control solenoid and the ECM.

    Repair: Repair the circuit.Verify that the repair eliminates the problem.

    STOP

Test Step 6. Compare "Fan Pump Pressure" to "Desired Fan Pump Pressure"

  1. Start the engine.

  1. Compare the status for "Fan Pump Pressure" to the status for "Desired Fan Pump Pressure" on ET.

  1. Turn the keyswitch to the OFF/RESET position.

Expected Result:

The status for "Fan Pump Pressure" should closely correlate with the status for "Desired Fan Pump Pressure".

Results:

  • OK - The system is functioning correctly.

    Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.

    STOP

  • Not OK - Proceed to Test Step 7.

Test Step 7. Measure the Current to the Fan Control Solenoid

  1. Reconnect the J1/P1 ECM connector.

  1. The J508/P508 fan control solenoid connector should still be disconnected. Install a jumper wire between J508:2 and P508:2.

  1. Connect an ammeter that is capable of withstanding a 5 Amp current between J508:1 and P508:1.

  1. Start the engine and observe the reading on the ammeter that is installed in the circuit.

  1. Turn the keyswitch to the OFF/RESET position.

  1. Remove the ammeter and the jumper wire from the circuit.

  1. Reconnect the J508/P508 fan control solenoid connector.

Expected Result:

The ECM should be supplying between 0.65 and 1.8 Amp to the fan control solenoid.

Results:

  • OK - The ECM appears to be supplying the correct current to the solenoid. Either the pump or the motor may not be responding correctly.

    Repair: Troubleshoot the hydraulic system. Refer to Testing and Adjusting, "Hydraulic and Steering System".

    STOP

  • Not OK - The ECM may not be producing a valid supply.

    Repair: Verify your results.Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.Verify that the repair eliminates the problem.

    STOP

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