REFRIGERANT(for HFO-1234yf(R1234yf)) ON-VEHICLE INSPECTION

PROCEDURE

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   INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET

   Tip:

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

   
   

   1. Remove the cool air intake duct seal.

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

      
      

      • Doors are fully open.

      • The engine is idling.

      • The A/C switch is on.

      • The temperature is set to max cool.

      • The blower speed is set to high.

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

      
      
      1. 

         *a	LO
         *b	HI

         Normally functioning air conditioning system

         Table 1. Gauge Reading

         Pressure Side	Refrigerant Volume
         Low	150 to 250 kPa (1.5 to 2.5 kgf/cm2, 22 to 36 psi)
         High	1370 to 1570 kPa (14.0 to 16.0 kgf/cm2, 199 to 228 psi)

      2. Abnormally functioning air conditioning system

         
         
         1. 

            *a	LO
            *b	HI

            During operation, pressure on low pressure side cycles between normal and vacuum

            Symptom	Air conditioning system periodically cools and then fails to cool
            Probable Cause	Moisture in air conditioning system freezes at expansion valve orifice, causing refrigerant to temporarily stop circulating
            	After system stops and warms up again, ice melts and normal operation is temporarily restored
            Diagnosis	Cooler dryer (integrated into condenser tank) saturated with moisture
            	Moisture in air conditioning system is freezing at expansion valve orifice and blocking circulation of refrigerant
            Corrective Actions	Replace cooler dryer
            	Remove moisture by repeatedly evacuating air from air conditioning system
            	Recharge air conditioning system with proper amount of new or purified refrigerant

            Tip:

            For the example above, moisture is present in the air conditioning system.

         2. 

            *a	LO
            *b	HI

            Pressure is low on both low and high pressure sides

            Symptom	Air conditioning system does not cool effectively
            	Insufficient cooling performance
            Probable Cause	Refrigerant leaks from air conditioning system
            Diagnosis	Insufficient refrigerant
            	Refrigerant leaking
            Corrective Actions	Check for refrigerant leaks and repair if necessary
            	Recharge air conditioning system with proper amount of new or purified refrigerant
            	If gauges indicate pressure of close to 0, then it is necessary to evacuate air conditioning system after repairing leaks

            Tip:

            For the example above, there is insufficient refrigerant.

         3. 

            *a	LO
            *b	HI

            Pressure is low on both low and high pressure sides

            Symptom	Air conditioning system does not cool effectively
            	Frost exists on pipe from condenser to evaporator unit
            Probable Cause	Refrigerant flow is obstructed by dirt inside pipes of condenser core
            Diagnosis	Condenser is clogged
            Corrective Actions	Replace condenser

            Tip:

            For the example above, there is poor circulation of refrigerant.

         4. 

            *a	LO
            *b	HI

            Vacuum is indicated on low pressure side and very low pressure is indicated on high pressure side

            Symptom	Air conditioning system does not cool effectively (System may cool occasionally)
            	Frost or condensation is seen on piping on both sides of receiver/dryer or expansion valve
            Probable Cause	Refrigerant flow is obstructed by moisture or dirt in air conditioning system
            	Expansion valve is stuck closed
            Diagnosis	Refrigerant does not circulate
            Corrective Actions	Replace expansion valve
            	Replace condenser
            	Evacuate air conditioning system and recharge with proper amount of new or purified refrigerant

            Tip:

            For the example above, the refrigerant does not circulate.

         5. 

            *a	LO
            *b	HI

            Pressure is too high on both low and high pressure sides

            Symptom	Air conditioning system does not cool effectively
            Probable Cause	Unable to provide sufficient performance due to excessive amount of refrigerant
            	Cooling effectiveness of condenser is insufficient
            Diagnosis	Excessive amount of refrigerant in air conditioning system because excessive refrigerant was added during recharging
            	Cooling effectiveness of condenser is insufficient because condenser fins are clogged or cooling fan is faulty
            Corrective Actions	Clean condenser
            	Check operation of condenser cooling fan
            	If condenser is clean and fan operation is normal, check amount of refrigerant and recharge air conditioning system with proper amount of new or purified refrigerant

            Tip:

            For the example above, the air conditioning system is overcharged or cooling effectiveness of condenser is insufficient.

         6. 

            *a	LO
            *b	HI

            Pressure is too high on both low and high pressure sides

            Symptom	Air conditioning system does not cool
            	The low pressure piping is too hot to touch
            Probable Cause	Air in air conditioning system
            Diagnosis	Air present in air conditioning system
            	Insufficient vacuum purging when evacuating air conditioning system
            Corrective Actions	Replace cooler dryer
            	Check compressor oil to see if it is dirty or insufficient
            	Evacuate air conditioning system and recharge it with new or purified refrigerant

            Note:

            These gauge indications occur when the air conditioning system has been left open and then recharged without evacuating the system.

            Tip:

            For the example above, air is present in the air conditioning system.

         7. 

            *a	LO
            *b	HI

            Pressure is too high on both low and high pressure sides

            Symptom	Air conditioning system does not cool effectively
            	Frost or large amount of condensation on piping on low pressure side
            Probable Cause	Expansion valve may be stuck open or metering refrigerant incorrectly
            Diagnosis	Excessive refrigerant in low pressure piping
            	Expansion valve open too wide
            Corrective Actions	Replace expansion valve

            Tip:

            For the example above, there is an expansion valve malfunction.

         8. 

            *a	LO
            *b	HI

            Pressure is too high on both low and high pressure sides or pressure is too low on high pressure side

            Symptom	Air conditioning system does not cool effectively
            Probable Cause	Internal leak in compressor
            Diagnosis	Low compression
            	Leak from damaged valve or other compressor component
            Corrective Actions	Replace compressor

            Tip:

            For the example above, there is insufficient compressor compression.

      3. 

         *a	Pressure on Low Pressure Side kPa (kgf/cm2, psi)	*b	Pressure on High Pressure Side kPa (kgf/cm2, psi)
         *c	Blower High Zone	*d	Blower Low Zone

         Gauge readings (Reference)

   3. Install the cool air intake duct seal.

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