REFRIGERANT(for HFC-134a(R134a)) ON-VEHICLE INSPECTION

PROCEDURE

1. INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET

   Tech Tips

   The following examples show the readings of a manifold gauge set and the corresponding air conditioning system problems.

   
   

   1. Read the manifold gauge pressure when the following conditions are met:

      
      

      • Temperature at the air inlet with recirculate selected is 30 to 35°C (86 to 95°F).

      • The blower speed is set to high.

      • The temperature is set to max cool.

      • The A/C switch is on.

      • Doors are fully open.

      • The power switch is on (READY).

      
      

      1. 

         Normally functioning air conditioning system.

         Gauge Reading

         Pressure Side	Refrigerant Volume
         Low	0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm2, 21 to 36 psi)
         High	1.37 to 1.57 MPa (14 to 16 kgf/cm2, 199 to 228 psi)

      2. Moisture is present in the air conditioning system.

         

         *1	Condition: Air conditioning system periodically cools and then fails to cool.

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         During operation, pressure on low pressure side cycles between normal and vacuum	Moisture in air conditioning system freezes at the expansion valve orifice, causing refrigerant to temporarily stop circulating After the system stops, and warms up again, ice melts and normal operation is temporarily restored	Cooler dryer (integrated into condenser tank) saturated with moisture Moisture in the air conditioning system freezes at expansion valve orifice and blocks circulation of refrigerant	Replace cooler dryer Remove moisture by repeatedly evacuating air from the air conditioning system Recharge the air conditioning system with the proper amount of new or purified refrigerant

      3. Insufficient refrigerant

         

         *1	Condition: Air conditioning system does not cool effectively.

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         Pressure is low on both low and high pressure sides Insufficient cooling performance	Refrigeration leaks from the system	Insufficient refrigerant Refrigerant leaking	Check for refrigerant leaks and repair if necessary Recharge the air conditioning system with the proper amount of new or purified refrigerant If the gauges indicate pressure of close to 0, then it is necessary to evacuate air conditioning system after repairing the leak

      4. Poor circulation of refrigerant

         

         *1	Condition: Air conditioning system does not cool effectively.

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         Pressure is low on both low and high pressure sides Frost exists on pipe from condenser to evaporator unit	Refrigerant flow is obstructed by dirt inside the pipes of the condenser core	Condenser is clogged	Replace condenser

      5. Refrigerant does not circulate.

         

         *1	Condition: Air conditioning system does not cool. (System may cool occasionally.)

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         Vacuum is indicated on low pressure side and very low pressure is indicated on high pressure side Frost or condensation is seen on piping on both sides of receiver/dryer or expansion valve	Refrigerant flow is obstructed by moisture or dirt in air conditioning system Expansion valve is stuck closed	Refrigerant does not circulate	Replace expansion valve Replace condenser Evacuate air conditioning system and supply the proper amount of new or purified refrigerant

      6. Air conditioning system is overcharged or cooling effectiveness of condenser is insufficient.

         

         *1	Condition: Air conditioning system does not cool effectively.

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         Pressure is too high on both low and high pressure sides	Unable to develop sufficient performance due to excessive amount of refrigerant Cooling effectiveness of condenser is insufficient	Excessive amount of refrigerant in air conditioning system → excessive refrigerant was added during recharging Condenser cooling effectiveness is insufficient → condenser fins are clogged or cooling fan is faulty	Clean condenser Check the operation of condenser cooling fan If 1 and 2 are normal, check the amount of refrigerant and recharge the air conditioning system with the proper amount of new or purified refrigerant

      7. Air is present in the air conditioning system.

         

         *1	Condition: Air conditioning system does not cool.
         *2	NOTE: These gauge indications occur when the air conditioning system has been left open and then recharged without evacuating the system

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         Pressure is too high on both low and high pressure sides The low pressure piping is too hot to touch	Air in air conditioning system	Air present in air conditioning system Insufficient vacuum purging when evacuating the air conditioning system	Replace cooler drier Check compressor oil to see if it is dirty or insufficient Evacuate the air conditioning system and recharge it with new or purified refrigerant

      8. Expansion valve malfunction

         

         *1	Condition: Air conditioning system does not cool effectively.

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         Pressure is too high on both low and high pressure sides Frost or a large amount of condensation on piping on low pressure side	Expansion valve may be stuck open or metering refrigerant incorrectly	Excessive refrigerant in low pressure piping Expansion valve open too wide	Replace expansion valve

      9. Insufficient compressor compression

         

         *1	Condition: Air conditioning system does not cool.

         Symptom	Probable Cause	Diagnosis	Corrective Actions
         Pressure is too high on both low and high pressure sides Pressure is too low on high pressure side	Internal leak in compressor	Low compression Leak from a damaged valve or other compressor component	Replace compressor

         Gauge readings (Reference)