Automatic Temperature Control Troubleshooting Codes
Use this procedure to troubleshoot the performance of the HVAC system for machines equipped with automatic temperature control.
Connect "Cat"® Electronic Technician (Cat® ET) and check for diagnostics associated with the HVAC system. Refer to the Machine Troubleshooting Guide if any of the following codes are active.
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| Illustration 1 | g03090916 |
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HVAC Diagnostic Codes | |
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| Illustration 2 | g03090917 |
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Typical HVAC ET status parameters and values | |
- Diagnostic Codes
- Low-Pressure Switch / High-Pressure Switch
- Low Refrigerant Charge
- Water Valve Actuator
- A/C Compressor
Connect "Cat"® ET to the service tool connector. Check for active diagnostic codes. Look for active codes that are related to the HVAC system in Illustration 1. Use the appropriate circuit test to troubleshoot any active codes before continuing.
Low-Pressure Switch / High-Pressure Switch
Use "Cat"® ET to monitor the "Air Conditioning Refrigerant Monitoring Circuit" status parameter. With a proper charge, the status should be closed. If the status is open, check the pressure switches and circuit (refer to the pressure switch tests section in this book).
Refer to Air Conditioning Performance - Test
Test the water value actuator control by switching to heat mode. Use Cat® ET and monitor the "Cab Air Heater Engine Coolant Actuator Duty Cycle" status parameter and rotate the temperature dial. The parameter should go to 5% when the temperature dial is full CCW and 95% when the temperature dial is full CW. If the "Cab Air Heater Engine Coolant Actuator Duty Cycle" doesn't move with the temperature dial, check the temperature dial. If "Cab Air Heater Engine Coolant Actuator Duty Cycle" moves with the temperature dial, verify that the water valve actuator circuit and the actuator rotate.
Switch to AC mode and use Cat ET to monitor the "A/C Compressor" status parameter with the engine running. If the compressor status does not turn to ON after 20 seconds, check the evaporation temperature circuit and the pressure switch circuits . Refer to Troubleshooting Guide , "Diagnostic Trouble Codes" and "HVAC, Control System". If the compressor status is ON and the compressor does not turn on, check for power at the compressor connection.
Note: If the compressor status is on and there is power at the compressor clutch, then replace the compressor.
- Diagnostic Codes
- Water Valve Actuator
Connect Cat ET to the service tool connector. Check for active diagnostic codes. Look for active codes that are related to the HVAC system in Illustration 1. Use the appropriate circuit test to troubleshoot any active codes before continuing.
Test the water value actuator control by switching to heat mode. Use Cat® ET and monitor the "Cab Air Heater Engine Coolant Actuator Duty Cycle" status parameter and rotate the temperature dial. The parameter should go to 5% when the temperature dial is full CCW and 95% when the temperature dial is full CW. If the "Cab Air Heater Engine Coolant Actuator Duty Cycle" doesn't move with the temperature dial, check the temperature dial. If "Cab Air Heater Engine Coolant Actuator Duty Cycle" moves with the temperature dial, verify that the water valve actuator circuit and the actuator rotate.