A/C System Test: Test
WARNING:
- 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.
NOTICE:
- 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.
- Connect an A/C recover/recycle/recharge machine, following equipment manufacturer's instructions.
The performance test will help determine if the A/C system is operating within specifications.
Performance Test
- A/C System - Inspect
Procedure
- Do the A/C system inspection - Refer to: A/C System Contamination Inspection or A/C System Test or A/C System Inspection , and correct any problems found.
- A/C System - Test
Preconditions
Procedure/Specifications
1. Determine the relative humidity and air temperature.
Figure 1
2. Insert a thermometer (a) in the center vent. (Figure 1)3. To measure the intake temperature, place a hygro-thermometer (b) as shown. (Figure 1)4. Test conditions:
- The blower intake temperature must be at least 68 deg.F (20 deg.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 transmission to P position/mode.
- Start the engine.
- Set the A/C system to the following conditions:
-
- A/C: ON
- Temperature control: MAX COOL (Lo)
- Mode control: VENT (
)
- Recirculation control: RECIRCULATE
- Fan control: Max
- All vents: Open
- Use the throttle pedal depressor tool to run the engine at a steady 1, 500 rpm.
- No driver or passengers in the 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 test conditions, read the delivery temperature from the thermometer in the dashboard center vent, the blower 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 (Figure 2):
- 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.Figure 2
8. To complete the high side (discharge) pressure/blower intake temperature chart (Figure 3):
- 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.Figure 3
9. To complete the low side (suction) pressure/blower intake temperature chart (Figure 4):
- 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.Figure 4
Pressure Test
- Refrigerant Pressure Check Procedure
Procedure/Specifications
- Check the value shown on the manifold gauge. If the value is out of the normal range, do proper troubleshooting and check it again.
- How to Read Gauge
Procedure/Specifications
- Check that the A/C system works properly.
NOTE: The illustration shows normal conditions at outside temperature 68 deg.F (20 deg.C). - A/C System Pressure - Test
Procedure/Specifications
Gauge Level Related Symptoms Probable Cause Suction pressure is low - Low refrigerant charge
- Expansion valve is not opened sufficiently
Suction line from expansion valve to A/C compressor is not cold Low refrigerant charge More than 18-29 deg.F (10-16 deg.C) temperature difference between A/C compressor inlet pipe and outlet pipe Refrigerant does not flow properly at A/C compressor internal passages, lines or components Vent temperature is too high Low refrigerant charge Large temperature difference between high/low pressure sides of A/C line or among components Refrigerant does not flow properly at A/C suction line, discharge line or components Pressure in A/C system is equalized with static pressure high after A/C compressor is stopped (4-12 hours after engine is off) - Gas in system is not compressed
- Incorrect refrigerant
A/C compressor or receiver pipe is not hot Debris is clogged at inlet side of condenser Gauge Level Related Symptoms Probable Cause Air coming from outlet is not cold enough Slightly low refrigerant charge - Pressures at suction and discharge lines are equalized quickly after A/C compressor is stopped
- Suction pressure is higher than normal
Faulty A/C compressor inside valve or valve seal - Excessive A/C compressor noise
- Pressure is equalized quickly and there is excessive noise after A/C compressor is stopped
A/C compressor internal damage (Check A/C system for debris) Air coming from outlet is not cold at all - Expansion valve is closed
- Receiver tank is clogged
- Evaporator is freezing
After refrigerant is added properly - Expansion valve is freezing
- Faulty expansion valve
Gauge Level Related Symptoms Probable Cause Air coming from outlet is not cold enough Expansion valve is open Suction pressure is turned to negative pressure because openings at expansion valve are freezing - Moisture in the system
- Faulty expansion valve
Suction pressure drops slightly when \"Recirculated\" airflow is switched to \"Fresh Air\" Expansion valve is clogged, stuck closed, or not opening sufficiently because of debris or desiccant Temperature of suction hose at A/C compressor is lower than outlet of expansion valve or evaporator Suction hose is deformed or clogged. Airflow through A/C condenser is weak or restricted - Dirty A/C condenser or damaged fins
- Debris between A/C condenser and radiator
- Faulty radiator or A/C condenser fan motor(s)
Temperature between A/C condenser inlet and outlet is less than about 9 deg.F (5 deg.C) when radiator and A/C condenser fan run at high speed, with doors opened and fresh air selected Gauge Level Related Symptoms Probable Cause Discharge pressure is reduced when A/C condenser is cooled Refrigerant overcharge - Airflow in VENT (
- Air temperature in VENT (
Faulty expansion valve - Suction pressure drops slightly when \"Recirculated\" airflow is switched to \"Fresh Air\"
- Discharge pressure is almost normal value
Expansion valve is stuck open or opened too long - A sheet of paper does not stick on to A/C condenser surface with the cooling fans on
- Temperature between A/C condenser inlet and outlet is less than about 9 deg.F (5 deg.C) when the radiator and A/C condenser fan run at high speed, with doors opened and fresh air selected
Radiator or A/C condenser fans circuit has a problem Belt type A/C compressor:A/C compressor clutch remains engaged when A/C system is stopped - Insufficient A/C compressor clutch clearance
- Faulty A/C compressor circuit
- Excessive air in system
- Pressure relief valve is opened