HOSE 5I4751 - Caterpillar

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, heck 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 Cab Air Heater Engine Coolant Actuator Duty Cycle" doesn't move with the temperature dial, check the temperature dial (see the troubleshooting section 2661 in the machine troubleshooting guide). If the Cab Air Heater Engine Coolant Actuator Duty Cycle" moves with the temperature dial, verify the water valve actuator circuit and that the actuator is rotating.A/C Compressor
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 (refer to 2357 diagnostic code in the machine TSG) and the pressure switch circuits (refer to the pressure switch tests section in this book). 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.Cab Temperature Low
Probable Causes
Diagnostic Codes
Water Valve ActuatorRecommended 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.Water 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 Cab Air Heater Engine Coolant Actuator Duty Cycle" doesn't move with the temperature dial, check the temperature dial (see the troubleshooting section 2661 in the machine troubleshooting guide). If the Cab Air Heater Engine Coolant Actuator Duty Cycle" moves with the temperature dial, verify the water valve actuator circuit and that the actuator is rotating.No airflow from Evaporator Blower Motor
No Auto Blower Control
Illustration 3 g03417195
Illustration 4 g03543956Perform this test with the key on. Use a 5P-7277 Voltage Tester or use a 9U-7330 Digital Multimeter and connect the negative probe