3412E Engine for Caterpillar Built Machines Coolant Flow - Test Caterpillar

System Operation Description:

Use this procedure to troubleshoot the electrical system if a problem is suspected with the coolant flow switch or if another procedure has directed you here.

The coolant flow switch is a reed switch that is used to detect the flow of coolant in the engine's cooling system.

Illustration 1	g01249790
Coolant flow switch (1) Flow switch assembly (2) Paddle

The coolant flow switch is a normally open switch. The contacts of flow switch assembly (1) close as coolant flow from the engine flows across paddle (2) of the switch. The Electronic Control Module (ECM) monitors the status of the coolant flow switch during engine operation. If the ECM detects a loss of coolant flow in the engine during operation, a signal will be sent in order to alert the operator of the condition.

The status of the "Engine Coolant Flow" can be monitored using AVSpare Electronic Technician (ET) in order to determine the state of the coolant flow switch.

Illustration 2	g01393020
Schematic for the coolant flow switch

Test Step 1. Verify that the Coolant Level is Correct

1. Ensure that the coolant level for the engine is correct. Refer to Troubleshooting, "Coolant Level is Low".

Expected Result:

The coolant level is OK.

Results:

• OK - The coolant level is OK. Proceed to Test Step 2.

• Not OK - The coolant level is low.

  Repair: Diagnose the reason for a low coolant level.Refer to Systems Operation/Testing and Adjusting, "Cooling System" for additional information.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Inspect the Electrical Connectors and the Wiring

1. Remove electrical power from the ECM.

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Illustration 3	g01393380
ECM (3) J1/P1 connectors (4) J2/P2 connectors

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Illustration 4	g01408060
Component locations (5) Coolant flow switch (6) Coolant temperature sensor

2. Thoroughly inspect connectors (3) and (4). Thoroughly inspect connector (5) for the coolant flow switch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

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Illustration 5	g01394770
Terminal locations at the P1 ECM connector for the coolant flow switch (P1-26) Coolant flow switch (P1-29) Sensor return

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Illustration 6	g01155187
Terminal locations at the connector for the coolant flow switch (Terminal 1) Switch signal (Terminal 2) Return

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

4. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

Expected Result:

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

Results:

• OK - The harness and wiring are OK. Proceed to Test Step 3.

• Not OK - There is a problem in the connectors and/or wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 3. Use Cat ET to Monitor the Switch Status

1. Connect Cat ET to the service tool connector.

2. Restore electrical power to the ECM.

3. Observe the status for "Engine Coolant Flow" on the Cat ET.

4. Start the engine.

5. Observe the status for "Engine Coolant Flow" on the Cat ET.

6. Remove electrical power from the ECM.

Expected Result:

Cat ET indicates "No Flow" while the engine is not running. Cat ET indicates "Flow" while the engine is running.

Results:

• OK - Cat ET indicates "No Flow" while the engine is not running. Cat ET indicates "Flow" while the engine is running.

  Repair: The switch is operating correctly at this time. There may be an intermittent problem with the switch or the switch circuit. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - Cat ET does not indicate "No Flow" while the engine is not running. Cat ET does not indicate "Flow" while the engine is running. Cat ET does not indicate the correct status for the coolant flow switch. Proceed to test step 4.

Test Step 4. Create a Short at the Connector for the Coolant Flow Switch

1. Disconnect the connector for the coolant flow switch.

2. Fabricate a jumper wire that is long enough to create a short at the harness connector for the coolant flow switch. Crimp connector pins to each end of the jumper wire.

3. Install the jumper wire to the terminals of the harness connector of the coolant level switch.

4. Restore electrical power to the ECM.

5. Observe the status of "Engine Coolant Flow" on Cat ET.

6. Remove electrical power from the ECM. Restore the wiring to the original configuration.

Expected Result:

The status indicates "Flow" with the jumper wire in place.

Results:

• OK - The status indicates "Flow" with the jumper wire in place. The ECM and the wiring are operating correctly. Proceed to Test Step 5.

• Not OK - The status indicates "No Flow" with the jumper wire in place. There is a problem in the harness between the ECM and the connector for the coolant flow switch. There may be a problem with the ECM. Proceed to Test Step 6.

Test Step 5. Check the Coolant Flow Switch

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Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.

1. Drain the engine coolant to a level that is below the coolant flow switch.

2. Remove the coolant flow switch from the engine.

3. Manually close the coolant flow switch. Ensure that the operation of the switch is smooth and ensure that the switch does not bind.

4. Check for continuity between the terminals of the switch at the connector while the switch is closed.

Expected Result:

The switch operates smoothly and there is continuity between the terminals at the connector while the switch is closed.

Results:

• OK - The switch operates smoothly and there is continuity between the terminals while the switch is closed.

  Repair: The switch and the switch circuit are operating correctly. There may be a mechanical problem with the cooling system of the engine. Diagnose the cooling system of the engine. Refer to Systems Operation/Testing and Adjusting, "Cooling System". Verify that the repair eliminates the problem.

  STOP

• Not OK - The switch does not operate smoothly or there is not continuity between the terminals while the switch is closed.

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

  STOP

Test Step 6. Check for the Correct Operation of the ECM

1. Remove electrical power from the ECM.

2. Disconnect the J1/P1 ECM connector.

3. Fabricate a jumper wire that is long enough to create a short between the ECM connector and the engine ground stud. Crimp a connector socket to one end of the jumper wire.

4. Remove the wire from terminal location P1-45 at the ECM connector. Install the jumper wire into this terminal location.

5. Reconnect the J1/P1 ECM connector.

6. Connect the other end of the jumper wire to the engine ground stud.

7. Restore electrical power to the engine ECM.

8. Observe the status of "Engine Coolant Flow" on Cat ET.

9. Remove the electrical power from the ECM. Restore the wiring to the original configuration.

Expected Result:

The status indicates "Flow" with the jumper wire in place.

Results:

• OK - The status indicates "Flow" with the jumper wire in place.

  Repair: There is an open circuit in the harness between the ECM connector and the connector for the coolant flow switch and/or there is an open circuit in the wire between engine ground and the connector for the coolant flow switch. Repair the wiring harness. Replace parts, if necessary. Verify that the repair eliminated the original problem.

  STOP

• Not OK - The status indicates "No Flow" with the jumper wire in place.

  Repair: The ECM is not detecting the correct switch status. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "ECM - Replace" for the correct procedure. Verify that the repair eliminates the problem.

  STOP