Insufficient Cooling; No Cooling; Intermittent Cooling
Symptom: Insufficient Cooling; No Cooling; Intermittent CoolingStep 1 Checking refrigerant charge
1. Run the engine at a fast idle.
2. Operate the air conditioner at maximum cooling for a few minutes.
3. Determine the amount of refrigerant as shown by observing the sight glass.
Step 2 Checking refrigerant pressure
1. Connect the manifold gauge set.
2. Operate the engine at 1,500 rpm and set the air conditioner to maximum cooling.
3. Measure the low and high pressures.
Specified pressure at 25°C (77°F)
Low pressure: 98 - 167 kPa (1.0 - 1.7 kg/cm2, 14 - 24 psi)
High pressure: 1,030 - 1,275 kPa (10.5 - 13.0 kg/cm2, 149 - 185 psi)
4. If the pressure is not as specified, refer to the following items and check the system.
Case 1
Measured pressure
Low pressure: Below 78 kPa (0.8 kg/cm2, 11 psi)
High pressure: 785 - 883 kPa (8 - 9 kg/cm2, 114 - 128 psi)
Possible cause: Insufficient refrigerant
Condition:
^ Outlet air from vents not cold
^ Bubbles seen in sight glass
Step 1
1. Check for oil stains on the pipes, hoses and other parts.
2. If oil staining is found at the connection of pipes or hoses, replace the 0-ring; then, evacuate, charge, and test the system.
3. If oil staining is not found, go to Step 2.
Step 2
1. Check for leakage from connections with a gas leak tester.
^ Inlet and outlet of condenser
^ Inlet and outlet of receiver/drier
^ Inlet and outlet of compressor
^ Sight glass
^ Inlet and outlet of cooling unit
2. If leakage is evident, go to Step 3.
3. If leakage cannot be found, evacuate, charge, and test the system.
(System OK, but refrigerant leaked gradually over time.)
Step 3
1. Check tightening torque of the connection where leak was detected.
2. If the connection is loose, tighten the connection; then, evacuate, charge, and test the system.
3. If the connection is properly tightened, replace the 0-ring; then, evacuate, charge, and test the system.
Case 2
Measured pressure
Low pressure: Above 245 kPa (2.5 kg/cm2, 36 psi)
High pressure: Above 1,962 kPa (20 kg/cm2, 284 psi)
Possible cause: Excessive refrigerant or insufficient condenser cooling
Condition: Insufficient cooling
Step 1
1. Check the condenser for bent fins or damage.
Repair or replace if necessary.
2. If the condenser is OK, go to Step 2.
Step 2
1. Discharge the excessive refrigerant.
WARNING: Always wear gloves and eye protection when discharging the refrigerant.
2. Verify that the refrigerant pressure is normal.
Case 3
Measured pressure
Low pressure: Above 245 kPa (2.5 kg/cm2, 36 psi)
High pressure: Above 2,256 kPa (23 kg/cm2, 327 psi)
Possible cause: Air in system
Condition: Insufficient cooling
Step 1
- Discharge the refrigeration system.
Step 2
- Evacuate the system to remove all air from the system.
Step 3
- Charge the system with refrigerant.
Step 4
- After charging, check the refrigerant pressure.
Step 5
- If low and high pressures are still too high, replace the receiver/drier.
Case 4
Measured pressure
Low pressure: 50 cm.Hg (2.0 cm.Hg) of Vacuum -147 kPa (1.5 kg/cm2, 21 psi)
High pressure: 687 - 1,472 kPa (7 - 15 kg/cm2, 100 - 213 psi)
Possible cause: Moisture in system
Condition: Intermittent cooling
(Moisture in refrigeration system freezes in expansion valve and causes temporary blocking. After time, ice melts and condition returns to normal.)
Step 1
- Discharge the refrigeration system.
Step 2
- Evacuate the system to remove all air and moisture from the system.
Step 3
- Charge the system with refrigerant.
Step 4
- After charging, check the refrigerant pressure.
Step 5
- If low and high pressures are not normal, replace the receiver/drier.
Case 5
Measured pressure
Low pressure: 76 cm.Hg (3.0 in.Hg) Vacuum
High pressure: Below 589 kPa (6 kg/cm2, 85 psi)
Possible cause: No refrigerant circulation
Condition: Refrigerant flow obstructed by moisture or dirt, causing freezing or blockage of expansion valve
Step 1
- Turn the air conditioner OFF for about 10 minutes. Turn the air conditioner ON to determine whether the blockage is due to moisture or dirt.
a) If caused by moisture, system will operate normally after being OFF for 10 minutes. (Ice melts and relives blockage).
If cause is moisture, refer to "Moisture in system."
b) If caused by dirt, system remains abnormal after being OFF 10 minutes.
If caused by dirt, go to Step 2.
Step 2
1. Remove the expansion valve.
2. Blow out the dirt with compressed air.
3. If unable to remove the dirt, replace the expansion valve.
4. Evacuate, charge, and test the system.
Case 6
Measured pressure
Low pressure: Above 245 kPa (2.5 kg/cm2, 36 psi)
High pressure: 1,864 - 1,962 kPa (19 - 20 kg/cm2, 270 - 284 psi)
Possible cause: Expansion valve stuck open
Condition: Insufficient cooling
1. Check whether there is frost or heavy dew on the suction pipe (between cooling unit and compressor).
2. If neither is found, refer to "Excessive refrigerant or insufficient condenser cooling".
3. If either is found, replace the expansion valve.
Case 7
Measured pressure
Low pressure: 392 - 589 kPa (4 - 6 kg/cm2, 51 - 85 psi)
High pressure: 687 - 981 kPa (7 - 10 kg/cm2, 100 - 142 psi)
Possible cause: Faulty compressor
Condition: No cooling
1. Run the engine at a first idle.
2. Check that the magnetic clutch is ON when the A/C switch and blower switch are ON.
3. If the magnetic clutch remains OFF, refer to the symptom flowchart, "Magnetic clutch does not operate". Magnetic Clutch Does Not Operate
4. If the magnetic clutch is ON, inspect the compressor.