A/C System Test
Special Tools Required
Image Description/Tool Number
6071777.png Big Digit Hygro-Thermometer PYR445703, commercially available
6071776.png Throttle Pedal Depressor Tool B240B, commercially available
Air conditioning refrigerant or lubricant vapor can irritate your eyes, nose, or throat.
Be careful when connecting service equipment.
Do not breathe refrigerant or vapor.

SRS components are located in this area. Review the SRS component locations and the precautions and procedures before doing repairs or service.

The performance test will help determine if the A/C system is operating within specifications.

NOTE:
If accidental system discharge occurs, ventilate the work area before resuming service.
Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.

Performance Test

1. A/C System - Inspect
1.
Do the A/C system inspection, and correct any problems found.
 

4. A/C System - Test
1.
Determine the relative humidity and air temperature.
2.
Insert a thermometer (A) in the center vent.
3.
Place a hygro-thermometer (B) near the blower unit's recirculation inlet duct.
4.
Test conditions:
The blower intake temperature must be at least 68 °F (20 °C).
Move the vehicle out of direct sunlight and let it cool down to the surrounding (ambient) temperature. If necessary, wash the vehicle to cool it down more quickly.
Open the hood.
Open the front doors.
Apply the parking brake.
Shift the vehicle to P, N position/mode, or Neutral.
Start the engine.
Set the A/C system to the following items.
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A/C: ON
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Temperature control: MAX COOL (Lo)
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Mode control: VENT
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Recirculation control: RECIRCULATE
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Fan control: Max
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All vents: Open
Use the throttle depressor tool to run the engine at a steady 1,500 rpm.
No driver or passengers in vehicle.
5.
Inspect the A/C components for the following conditions:
A/C compressor clutch not engaged.
Abnormal frost areas.
Unusual noises.
If you observe any of these conditions, refer to the Symptom Troubleshooting Index.
6.
After running the air conditioning for 10 minutes under the above test conditions, read the delivery temperature from the thermometer in the center vent, the intake temperature near the blower unit, and the discharge (high) and suction (low) pressures on the A/C gauges.





7.
To complete the vent (delivery)/blower intake temperature chart:
Mark the vent (delivery) temperature on the vertical line.
Mark the blower intake temperature on the bottom line.
Draw a vertical line from the blower intake temperature mark.
Draw a horizontal line from the vent (delivery) temperature mark until it intersects the vertical line.
NOTE: The vent (delivery) temperature and blower intake temperature should intersect in the shaded area. Any measurements outside the line may indicate the need for further inspection.
8.
To complete the high side (discharge) pressure/blower intake temperature chart:
Mark the high side (discharge) pressure on the vertical line.
Mark the blower intake temperature on the bottom line.
Draw a vertical line from the blower intake temperature mark.
Draw a horizontal line from the high side (discharge) pressure mark until it intersects the vertical line.
NOTE: The high side (discharge) pressure and blower intake temperature should intersect in the shaded area. Any measurements outside the line may indicate the need for further inspection.
9.
To complete the low side (suction) pressure/blower intake temperature chart:
Mark the low side (suction) pressure along the vertical line.
Mark the blower intake temperature along the bottom line.
Draw a vertical line from the blower intake temperature mark.
Draw a horizontal line from the low side (suction) pressure mark until it intersects the vertical line.
NOTE: The low side (suction) pressure and blower intake temperature should intersect in the shaded area. Any measurements outside the line may indicate the need for further inspection.


Pressure Test

5. A/C System 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
Discharge pressure abnormally High
Discharge pressure reduced when A/C condenser cooled with water spray
Significant refrigerant overcharge
Restricted/weak airflow through A/C condenser
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 9 °F (5 °C)
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
Evaporator freezing
Faulty evaporator temperature sensor (check DTC)
Faulty expansion valve or A/C compressor clutch relay stuck in the on position
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 9 °F (5 °C)
Radiator and/or A/C condenser fan motor(s) inoperative or wires reversed
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 stuck in the on position 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 18?29 °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 slightly Low
Vent temperature too high
Slightly low refrigerant charge
Air mix door sticking, misadjusted or inoperative
Excessive refrigerant oil in system
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