3512C Engines for 785C Off-Highway Trucks with Dynamic Gas Blending Caterpillar

Cooling Fan Speed - Test

Usage:

3512 8BR

Use this procedure to troubleshoot a problem with the cooling fan speed sensor. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

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Table 1
J1939 Code and Description	CDL Code and Description	Comments
1639-17 Fan Speed : Low - least severe (1)	E1363 (1) Low Engine Cooling Fan Speed	The code is logged.

The engine cooling fan speed sensor provides a signal to the Electronic Control Module (ECM). The ECM controls fan speed by varying the current to the fan control solenoid.

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Illustration 1	g06309292

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check the Status of the Engine Fan Speed A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Use Cat ET to perform the following override: -"Fan Override Test" C. Set the fan speed to 500 rpm. D. Use a 351-8635 Tachometer Kit to determine the actual speed of the fan. E. Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer. F. Deactivate the "Fan Override Test".	Fan Speed	Result: The engine fan speed is within ± 50 rpm. The sensor is operating correctly. There may be an intermittent electrical problem in a connector or in the harness. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect". Verify that the repair eliminated the problem. Result: The engine fan speed is not within ± 50 rpm. Proceed to Test Step 2.
2. Check the Sensor Supply Voltage at the Sensor Connector A. Turn the keyswitch to the OFF position. B. Disconnect the sensor connector from the wiring harness. C. Turn the keyswitch to the ON position. D. Measure the sensor supply voltage between the following terminals: - Terminal 2 and Terminal 3	Supply Voltage	Result: The supply voltage is reaching the sensor. Proceed to Test Step 3. Result: The supply voltage is not reaching the sensor. Repair: Refer to Troubleshooting, "Sensor Supply - Test" for additional information. Verify that the repair eliminated the problem.
3. Check the Signal Frequency at the Sensor Connector A. Turn the keyswitch to the OFF position. B. Remove the wire from terminal 1 on the sensor side of the connector. Connect the sensor connector. C. Connect Cat ET. D. Use Cat ET to perform the following override: -"Fan Override Test" E. Set the fan speed to 800 rpm. F. Use a multimeter to measure the frequency between the following: - Sensor signal wire and Engine ground G. Deactivate the "Fan Override Test". H. Turn the keyswitch to the OFF position. J. Restore all connectors and wiring to the original configuration.	Sensor Frequency	Result: The frequency is approximately 80 Hz. Note: Large Hydraulic Excavators use a frequency of 27Hz The engine cooling fan speed sensor is generating the correct signal. Repair: Repair or replace the wiring harness. Verify that the repair eliminated the problem. Note: Large Hydraulic Excavators use a frequency of 27Hz Result: The frequency is not approximately 80 Hz. Repair: Replace the fan drive assembly. Verify that the repair eliminated the problem.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).