Automotive Air Condition System Inspection with Manifold Gauge
1.Normal
If the refrigeration cycle is normal, the gauge pressure values are as shown.
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)
2.Insufficient refrigerant amount
3.Excessive refrigerant or insufficient condenser cooling
If there is excessive refrigerant or the condenser cooling is insufficient, the gauge pressure for the both the low-pressure and high-pressure side shows as being higher than the normal value.
(1)Symptom
Pressure is high at both low-pressure and high-pressure side.
Bubbles not observed in the sight-glass, even at low speed operation.
Insufficient cooling.
(2)Cause
Excessive refrigerant.
Poor condenser cooling.
(3)Remedy
Adjust to correct refrigerant amount.
Clean the condenser.
Inspect the vehicle cooling system (electric fan, etc.).
4.Moisture in refrigeration cycle
5.Compression defect in compressor
When a compression defect occurs in the compressor, the gauge pressure at the low-pressure side is higher than the normal value. The gauge pressure at the high-pressure side is lower than the normal value.
(1)Symptom
Low-pressure side is high, high-pressure side is low.
Turning off the air conditioner immediately restores the high-pressure side and low-pressure side to the same pressure.
Compressor unit is not hot to the touch.
Insufficient cooling.
(2)Cause
Compressor defect.
(3)Remedy
Inspect and repair the compressor.
Clog in refrigeration cycle
7.Air in refrigeration cycle
When air infiltrates the refrigeration cycle, the gauge pressure at both the low-pressure and high-pressure side is higher than the normal value.
(1)Symptom
Pressure is high at both low-pressure and high-pressure side.
Cooling performance decreases in proportion to the increase in the low-pressure.
If the refrigerant amount is correct, the flow of bubbles at the sight-glass is the same as during normal operation.
(2)Cause
Air infiltration.
(3)Remedy
Replace the refrigerant.
Implement thorough evacuation of the cycle.
8.Excess opening of expansion valve
