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Pressure Test

WARNING: This page is about a different car, the 2009 Acura MDX, 2008 Acura MDX, and 2007 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.
PRESSURE TEST REFERENCE CHART

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/cm2 , 28 psi) quickly, and then falls gradually. Air in system Recover, evacuate (see REFRIGERANT RECOVERY  ), and recharge with specified amount (see SYSTEM CHARGING  ).
Reduced or no airflow through A/C condenser.
  • Clogged 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 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 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.
Receiver/dryer outlet is cool, and inlet is warm (should be warm during operation). Clogged receiver/dryer Replace.
Suction pressure abnormally high Low-pressure hose and service port 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 fittings 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.
A/C fitting is dirty. Leaking O-ring Clean the A/C fitting and replace the O-ring.
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