TXV Air Conditioning (A/C) System Diagnosis (Reference Table)

Symptom		Correction
Low Side Pressure	High Side Pressure	Correction
150-300 kPa (21-43 psi)	1275-1670 kPa (185-244 psi)	Normal
Vacuum	500-600 kPa (71-85 psi)	Expansion valve is frozen or clogged. Heat sensing tube leaking, preventing refrigerant flow. Frost may be on tubing between the receiver/dryer and the expansion valve. Replace the expansion valve and the receiver dryer, and evacuate and recharge the system. Refer to the following: Thermal Expansion Valve Replacement Receiver Dehydrator Replacement Refrigerant Recovery and Recharging
Normal to vacuum	Normal to 690-980 kPa (100-142 psi)	The expansion valve is frozen due to moisture in the system, temporarily shutting down the refrigeration cycle. Replace the expansion valve and the receiver dryer, and evacuate and recharge the system. Refer to the following: Thermal Expansion Valve Replacement Receiver Dehydrator Replacement Refrigerant Recovery and Recharging
50-100 kPa (4-14 psi)	690-980 kPa (100-142 psi)	Insufficient refrigerant in system. Leak test the system, repair and recharge. Refer to Leak Testing and Refrigerant Recovery and Recharging .
400-600 kPa (57-85 psi)	690-980 kPa (100-142 psi)	Internal leak in compressor. Replace the compressor. Refer to Compressor Replacement .
250-300 kPa (36-43 psi)	1960-2450 kPa (285-355 psi)	System overcharged. Refer to Refrigerant Recovery and Recharging . Condenser fan malfunction. Refer to Cooling Fan Inoperative (Inoperative in Low Speed) or Cooling Fan Inoperative (Inoperative in High and Low Speeds) or Cooling Fan Inoperative (Inoperative in High Speed) or Cooling Fan Inoperative (Low Speed Operates in High Speed) in Engine Cooling. Condenser airflow restricted. Clean or repair the condenser as necessary. Refer to Condenser Replacement . Engine overheating. Refer to Engine Overheating in Engine Cooling. Air in A/C system due to improper evacuating. Replace the receiver dryer and evacuate and recharge the system. Refer to Receiver Dehydrator Replacement and Refrigerant Recovery and Recharging .
300-400 kPa (43-57 psi)	1960-2450 kPa (285-355 psi)	Expansion valve malfunction. Replace the expansion valve. Refer to Thermal Expansion Valve Replacement . Refrigerant flow not regulated properly. Frost may be on low side tubing.
Normal to low	Low	Low side restriction. Inspect for a kinked tube/hose, or a clogged suction screen.
Normal to low	Normal to high	High side restriction. Visually inspect for frost spot. Feel along tubing for temperature change.
Center Outlet Air Temperature Above Specifications		Improper refrigerant charge. Evacuate and recharge the system. Refer to Refrigerant Recovery and Recharging . Evaporator airflow restricted. Clean or repair the evaporator as necessary. Refer to Evaporator Core Replacement . Air leakage within the heater case. Refer to Air Delivery Improper . Temperature control door malfunction. Refer to Temperature Control Cable Adjustment . Compressor malfunction. Replace the compressor. Refer to Compressor Replacement .
Center Outlet Air Temperature Below Specifications		Insufficient air volume. Refer to Symptoms - HVAC Systems - Manual . Evaporator temperature sensor malfunction. Refer to Symptoms - HVAC Systems - Manual .