On-Vehicle Inspection

Test conditions:

• Temperature at the air inlet is 30 to 35°C (86 to 95°F).
• Engine is running at 1,500 RPM.
• All doors are fully open.
• Blower speed control switch is at HI.
• Temperature control switch is at MAX. COOL.
• A/C switch is ON.

Fig 1: Refrigerant Pressure Graph

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1. Normally functioning refrigeration system

   Gauge reading 

   REFRIGERANT FUNCTION REFERENCE
   
   

   Pressure side	Refrigerant volume
   Low	0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm2 )
   High	1.37 to 1.57 MPa (14 to 16 kgf/cm2 )

2. The A/C system periodically changes between normal and improper function due to moisture in the refrigerant system.
   Fig 2: Identifying Gauge Reading - Normally Functioning Refrigeration System

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   Fig 3: Identifying Gauge Reading - Periodically Cools And Fails

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptoms	Probable Cause	Diagnosis	Corrective Actions
   During operation, pressure on low - pressure side cycles between normal and vacuum	Moisture in refrigeration system freezes at expansion valve orifice, causing temporary stop of cycle. However, when melted, normal state is restored	Drier is overly saturated Moisture in refrigeration system freezes at expansion valve orifice and blocks refrigerant circulation	Replace cooler drier Remove moisture from cycle by repeatedly evacuating air Supply appropriate volume of new refrigerant

3. The A/C system does not function effectively due to insufficient cooling.
   Fig 4: Checking Refrigerant Pressure - A/C System Does Not Function Effectively Due To Insufficient Cooling

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptom	Probable Cause	Diagnosis	Corrective Actions
   Pressure low on both low and high-pressure sides Cooling performance insufficient	Gas leakage from refrigeration system	Insufficient refrigerant Refrigerant leakage	Check for gas leakage and repair if necessary Supply appropriate volume of new refrigerant If indicated pressure value close to 0 when connected to gauge, create vacuum after inspecting and repairing the location of leakage

4. The A/C system does not function effectively due to poor circulation of the refrigerant.
   Fig 5: Checking Refrigerant Pressure - A/C System Does Not Function Effectively Due To Poor Circulation Of Refrigerant

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptoms	Probable Cause	Diagnosis	Corrective Actions
   Pressure low on both low and high-pressure sides Frost exists on piping from condenser to A/C unit	Refrigerant flow obstructed by dirt in condenser	Condenser clogged	Replace condenser

5. The A/C system does not function intermittently because the refrigerant does not circulate.
   Fig 6: Checking Refrigerant Pressure - A/C System Does Not Function Intermittently Because Refrigerant Does Not Circulate

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptoms	Probable Cause	Diagnosis	Corrective Actions
   Vacuum indicated on low-pressure side, and extremely low pressure indicated on high-pressure side Frost or condensation seen on piping on both sides of condenser or expansion valve	Refrigerant flow obstructed by moisture or dirt in refrigeration system Refrigerant flow obstructed by gas leakage from expansion valve	Refrigerant does not circulate	Check expansion valve Clean expansion valve by blowing air Replace condenser Evacuate air and charge appropriate volume of new refrigerant For gas leakage from expansion valve, replace expansion valve

6. The A/C system does not function effectively due to overcharged refrigerant or insufficient cooling of the condenser.
   Fig 7: Checking Refrigerant Pressure - A/C System Does Not Function Effectively Due To Overcharged Refrigerant Or Insufficient Cooling Of Condenser

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptoms	Probable Cause	Diagnosis	Corrective Actions
   Pressure extremely high on both low and high-pressure sides	Excessive refrigerant Cooling performance of condenser insufficient	Condenser is dirty Condenser fan motor is malfunctioning Excessive refrigerant	Clean condenser Check condenser fan motor operation If 1 and 2 normal, check the amount of refrigerant and supply appropriate volume of refrigerant

7. The A/C system does not function due to air in the refrigeration system.
   CAUTION: The low-pressure piping may be very hot and cause serious burns.
   Fig 8: Checking Refrigerant Pressure -- A/C System Does Not Function Due To Air In Refrigeration System

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptoms	Probable Cause	Diagnosis	Corrective Actions
   Pressure extremely high on both low and high-pressure sides The low-pressure piping is too hot to touch	Air in refrigeration system	Air in refrigeration system Vacuum purging insufficient	Check if compressor oil is dirty or insufficient Evacuate air and charge new refrigerant

8. The A/C system does not function effectively due to an expansion valve malfunction.
   Fig 9: Checking Refrigerant Pressure - A/C System Does Not Function Effectively Due To An Expansion Valve Malfunction

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptoms	Probable Cause	Diagnosis	Corrective Actions
   Pressure extremely high on both low and high-pressure sides Frost or condensation on piping on low-pressure side	Problem with expansion valve	Excessive refrigerant in low pressure piping Expansion valve too wide open	Replace expansion valve

9. The A/C system does not function due to a defective compressor.
   Fig 10: Checking Refrigerant Pressure -- A/C System Does Not Function Due To A Defective Compressor

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   REFRIGERANT PRESSURE REFERENCE
   
   

   Symptoms	Probable Cause	Diagnosis	Corrective Actions
   Pressure extremely high on both low and high-pressure sides Pressure extremely low on high-pressure side	Internal leakage in compressor	Compression failure Leakage from damaged valve or broken sliding parts	Repair or replace compressor

   Gauge readings (Reference)

   Fig 11: Refrigerant Pressure Graph

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002