REFRIGERANT ON-VEHICLE INSPECTION

This is a method to specify trouble areas by using a manifold gauge set. Read the manifold gauge pressure under the following conditions.

Test conditions:

• Engine has been warmed up.

• All doors are fully open.

• Switch A/C ON.

• Blower switch is turned to ON.

• Engine is running at 1,500 rpm.

• Air inlet mode damper is set at recirculation.

• Temperature control lever is in MAX. COLD position.

• Air temperature at the air inlet is 20 to 35°C (68 to 95°F).

1. 

   When the refrigerant volume is correct, the gauge reading indicates as follow:

   Low pressure side
   0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm2)

   High pressure side
   1.37 to 1.57 MPa (14 to 16 kgf/cm2)

   Tech Tips

   Pressure varies under certain circumstances (outside air temperature, sunlight and wind).

2. When there is moisture in the refrigeration system:

   

   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 interuption of cycle However, when melted, returns to normal condition	Receiver dryer oversaturated Moisture in refrigeration system freezes at expansion valve orifice and blocks refrigerant circulation	Replace receiver dryer Remove moisture from cycle by repeatedly evacuating air Supply appropriate volume of new refrigerant

3. When cooling is insufficient:

   

   Symptoms	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 using gas leak detector, 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 location of leakage

4. When the circulation of the refrigerant is poor:

   

   Symptoms	Probable Cause	Diagnosis	Corrective Action
   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. When the refrigerant does not circulate:

   

   Symptoms	Probable Causes	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 with compressed air Replace condenser Evacuate air and then supply appropriate volume of new refrigerant For gas leakage from expansion valve, replace expansion valve

6. When the refrigerant is overcharged or cooling of condenser is insufficient:

   

   Symptoms	Probable Causes	Diagnosis	Corrective Actions
   Pressure extremely high on both sides	Excessive refrigerant Cooling performance of condenser insufficient	Excessive refrigerant Cooling performance of condenser insufficient	Clean condenser fins Check condenser fan motor operation to switch A/C ON If 1 and 2 normal, check amount of refrigerant and supply appropriate volume of refrigerant

7. When there is air in the refrigeration system:

   

   Symptoms	Probable Causes	Diagnosis	Corrective Actions
   Pressure extremely high on both low and high pressure sides Low pressure piping too hot to touch	Air in refrigeration system	Air in refrigeration system Insufficient vacuum purging	Check whether compressor oil dirty or insufficient Evacuate air and supply new refrigerant

8. When the expansion valve malfunctions:

   

   Symptoms	Probable Causes	Diagnosis	Corrective Actions
   Pressure extremely high on both low and high pressure sides Frost or condensation on piping on low pressure side	Expansion valve malfunction	Excessive refrigerant in low pressure piping Expansion valve opening too wide	Replace expansion valve

9. When the compressor is defective:

   

   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 of compressor Leakage from damaged valve or broken sliding parts in compressor	Repair or replace compressor