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Pressure Test

PRESSURE TEST

Test results Related symptoms Probable causes Remedy
Discharge (high) pressure abnormally high After stopping A/C compressor, pressure drops about 196 kPa (2.0 kgf/cm2 , 28 psi) quickly, and then falls gradually. Air in system Recover, evacuate (see SYSTEM EVACUATION ), and recharge with specified amount (see SYSTEM CHARGING ).
Reduced or no airflow through A/C condenser.
  • Clogged condenser or radiator fins
  • 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 High and low-pressures are balanced soon after stopping A/C compressor. Low side is higher than normal.
  • Faulty compressor discharge valve
  • Faulty 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 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.
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.
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