Pressure Test
Test results | Related symptoms | Probable cause | Remedy
--- | --- | --- | ---
Discharge (high) pressure abnormally high | After stopping A/C compressor, pressure drops about 196 kPa (2.0 kgf/cm 2 , 28 psi) quickly, and then falls gradually. | Air in system | Recover, evacuate, and recharge with specified amount.
No bubbles in sight glass when A/C condenser is cooled by water | Excessive refrigerant in system | Recover, evacuate, and recharge with specified amount.
Reduced or no airflow through A/C condenser | Clogged A/C condenser or radiator fins A/C condenser or radiator fan not working properly | Clean Check voltage and fan rpm. Check fan direction.
Line to A/C condenser is excessively hot. | Restricted flow of refrigerant in system | Restricted lines
Discharge pressure abnormally low | Excessive bubbles in sight glass; A/C condenser is not hot. | Insufficient refrigerant in system | Check for leak. Charge system.
High and low-pressures are balanced soon after stopping A/C compressor. Low side is higher than normal. | Faulty A/C compressor discharge valve Faulty A/C compressor seal | Replace the A/C compressor.
Outlet of expansion valve is not frosted, low-pressure gauge indicates vacuum. | Faulty expansion valve Moisture in system | Replace Recover, evacuate, and recharge with specified amount.
Suction (low) pressure abnormally low | Excessive bubbles in sight glass; A/C condenser is not hot. | Insufficient refrigerant in system | Repair the leaks. Recover, evacuate, and recharge with specified amount. Charge as required.
Expansion valve is not frosted, and low-pressure line is not cold. Low-pressure gauge indicates vacuum. | Frozen expansion valve (Moisture in system) Faulty expansion valve | Recover, evacuate, and recharge with specified amount. Replace the expansion valve.
Discharge temperature is low, and the airflow from vents is restricted. | Frozen evaporator | Run the fan with A/C compressor off, then check evaporator temperature sensor .
Expansion valve is frosted. | Clogged expansion valve | Clean or replace.
Suction pressure abnormally high | Low-pressure hose and check joint are cooler than the temperature around evaporator. | Expansion valve open too long | Repair or replace.
Suction pressure is lowered when A/C condenser is cooled by water. | Excessive refrigerant in system | Recover, evacuate, and recharge with specified amount.
High and low-pressures are equalized as soon as the A/C compressor is stopped, and both gauges fluctuate while running. | Faulty gasket Faulty high-pressure valve Foreign particle stuck in high-pressure valve | Replace the A/C compressor.
Suction and discharge pressures abnormally high | Reduced airflow through A/C condenser. | Clogged A/C condenser or radiator fins A/C condenser or radiator fan not working properly | Clean Check voltage and fan rpm. Check fan direction.
No bubbles in sight glass when A/C condenser is cooled by water | Excessive refrigerant in system | Recover, evacuate, and recharge with specified amount.
Suction and discharge pressures abnormally low | Low-pressure hose and metal end areas are cooler than evaporator. | Clogged or kinked low-pressure hose parts | Repair or replace.
Temperature around expansion valve is too low compared with that around receiver/dryer. | Clogged high-pressure line | Repair or replace.
Refrigerant leaks | A/C compressor clutch is dirty. | A/C compressor shaft seal leaking | Replace the A/C compressor.
A/C compressor bolt(s) are dirty. | Leaking around bolt(s) | Tighten bolt(s) or replace A/C compressor.
A/C compressor gasket is wet with oil. | Gasket leaking | Replace the A/C compressor.