Pressure Test

Test results	Related symptoms	Probable cause
Driver and passenger's side A/C vent temperatures may vary by approximately 20°F (11 °C) or more	Suction pressure may be low	Low refrigerant charge Expansion valve not opening sufficiently
	Driver's or passenger's air mix door DTCs present	One air mix door stuck or inoperative
Discharge pressure abnormally High	Discharge pressure reduced when A/C condenser cooled with water spray With doors open, fresh air selected and radiator and A/C condenser fan run on high speed, temperature drop across A/C condenser inlet to outlet is less than about 41°F (5 °C)	Significant refrigerant overcharge
Discharge pressure abnormally High	Restricted/weak airflow through A/C condenser	Dirty A/C condenser or damaged fins Debris between A/C condenser and radiator One or more cooling fans malfunctioning
Discharge pressure abnormally Low	Suction and discharge pressures equalize rapidly after stopping A/C compressor Suction pressure higher than normal	Faulty A/C compressor discharge valve or seal
Suction pressure abnormally Low	Weak or insufficient airflow across evaporator	Restricted blower intake or dust and pollen filter
	Suction pressure varies from near normal to a vacuum, as moisture freezes in expansion valve orifice	Moisture in the system Faulty expansion valve
	Reduced airflow from vents Vent temperature is very low	Condensation freezing on evaporator Faulty evaporator temperature sensor (check DTC) Faulty expansion valve or A/C compressor clutch relay
Suction pressure abnormally High	Lack of slight suction pressure variation at 1, 500 RPM when "Recirculated" airflow is switched to "Fresh Air" Discharge pressure near normal	Expansion valve stuck open or open too long
Suction and Discharge pressures abnormally High	Sheet of paper does not stick to front of A/C condenser surface with cooling fans on With doors open, fresh air selected and radiator and A/C condenser fan run on high speed, temperature drop across A/C condenser inlet to outlet is less than about 41°F (5 °C)	One (or both) cooling fan motor inoperative or wires reversed
Suction and Discharge pressures abnormally High	A/C compressor clutch remains engaged during off cycle Pressure relief valve may open	Insufficient A/C compressor clutch clearance A/C compressor clutch relay or circuit problem Excessive air in system
Suction and Discharge pressures abnormally Low	Suction line from expansion valve to A/C compressor is not cold	Excessively low refrigerant charge
	Lack of slight suction pressure variation at 1, 500 RPM when "Recirculated" airflow is switched to "Fresh Air"	Expansion valve clogged with debris/desiccant, stuck closed, or not opening sufficiently
	More than 50-60°F (10-16 °C) temperature drop across A/C condenser inlet to outlet pipes	Blocked or restricted A/C condenser internal passages or lines/components restricting refrigerant flow
	Significant temperature difference along high or low side A/C lines or components NOTE: Some restrictions may not show up until 3, 000 RPM)	Restriction in A/C suction or discharge lines or components (check temperatures to isolate)
Suction pressure High and Discharge pressure Low	Excessive A/C compressor noise Pressures equalize quickly and noise after A/C compressor turns off	A/C compressor internal damage (Check for A/C system debris contamination)
Suction and discharge pressures normal (or near normal)	Vent temperature too high	Slightly low refrigerant charge Air mix door sticking, misadjusted or inoperative Excessive refrigerant oil in system
Suction and discharge pressures normal (or near normal)	Static pressures high with A/C system equalized. (After engine is off 4- 12 hours)	Air/Non-condensable gasses in system Contaminated or incorrect refrigerant