CUTTING EDGE 5A8644 - Caterpillar

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.
Illustration 1 g03090916
HVAC Diagnostic Codes
Illustration 2 g03090917
Typical HVAC ET status parameters and values
Symptom Troubleshooting
Cab Temperature is High
Probable Causes
Diagnostic Codes
Low Pressure Switch / High Pressure Switch
Low Refrigerant Charge
Water Valve Actuator
A/C CompressorRecommended Actions
Diagnostic Codes
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).Low Refrigerant Charge
Refer to Air Conditioning Performance - TestWater Valve Actuator
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 while rotating 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 duty cycle of the "Cab Air Heater Engine Coolant Actuator" does not change in response to the