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A/C Performance Test

WARNING: This page is about a different car, the 2009 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Refer to the applicable warnings and cautions for this system before performing the following operation. See Heating and Air Conditioning/Plumbing - Warning  also,see Heating and Air Conditioning/Plumbing - Caution . Failure to follow these instructions may result in possible serious or fatal injury.
CAUTION: The use of an A/C recycling/charging station for purposes of determining the actual charge level of an A/C system is not recommend. Service recycling/charging stations do not reflect the correct amount of refrigerant charge in the A/C system after a single "reclaim" cycle. Tests have shown that it can take two or more "reclaim" cycles to remove all of the refrigerant charge, depending on the equipment being used. Use only the following procedure for determining the proper charge level.
NOTE: When connecting the service equipment coupling to the line fitting, verify that the valve of the coupling is fully closed. This will reduce the amount of effort required to make the connection.
  1. Check for any Diagnostic Trouble Codes using a scan tool. If no DTCs are found in the Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application, go to  2. If any DTCs are found, repair as required, then proceed to  2.
  2. Connect a tachometer and a manifold gauge set or an A/C recycling/charging station.
    NOTE: The ambient air temperature of the vehicle and the location where the vehicle will be tested must be a minimum of 21° C (70° F) before performing this test. Also the evaporator temperature sensor must be a minimum of 18° C (65° F) for this test as well. Place the vehicle in the testing area until the temperature within the vehicle reaches a minimum of 18° C (65° F).
  3. Operate the heating-A/C system under the following conditions.
    • Engine at 1,000 rpm at operating temperature
    • Door or windows open
    • Transmission in Park or Neutral with parking brake set (depending on transmission application)
    • A/C-heater controls set to Recirculation mode (max-A/C), full cool, panel mode, high blower and with A/C compressor engaged. If the A/C compressor does not engage, refer to A/C System Diagnosis, see A/C SYSTEM DIAGNOSIS .
  4. Insert a thermometer in the driver side center panel air outlet and operate the vehicle a minimum of ten minutes to allow the thermometer temperature to stabilize.
    NOTE: This procedure requires the technician to know what the temperature and relative humidity is at the time of the test. The temperature must be combined with the relative humidity to calculate the apparent ambient air temperature, when temperatures are above 21° C (70° F). Use the current ambient temperature and the relative humidity in your location. This information can be obtained from multiple sources, such as the internet or local news media.
  5. With the A/C compressor clutch engaged, compare the air temperature at the center panel outlet and the A/C compressor discharge pressure (high side) to the A/C Performance Temperature and Pressure chart. The A/C clutch may cycle, depending upon the ambient temperature and humidity. If the A/C clutch cycles, use the readings obtained before the clutch disengaged.
    A/C PERFORMANCE TEMPERATURE AND PRESSURE

    Ambient Air Temperature  21° C
    (70° F)    		 27° C
    (80° F)    		 32° C
    (90° F)    		 38° C
    (100° F)    		 43° C
    (110° F)
    Air Temperature at Center Panel Outlet  7° C
    (45° F)    		 7° C
    (45° F)    		 13° C
    (55° F)    		 13° C
    (55° F)    		 18° C
    (64° F)
    Compressor Inlet Pressure at Service Port (Low Side)  138 to 207 kPa
    (20 to 30 psi)    		 172 to 241 kPa
    (25 to 35 psi)    		 207 to 276 kPa
    (30 to 40 psi)    		 241 to 310 kPa
    (35 to 45 psi)    		 276 to 345 kPa
    (40 to 50 psi)
    Condensor Outlet Pressure at Service Port (High Side)  1034 to 1724 kPa
    (150 to 250 psi)    		 1379 to 2068 kPa
    (200 to 300 psi)    		 1724 to 2413 kPa
    (250 to 350 psi)    		 1999 to 2689 kPa
    (290 to 390 psi)    		 2413 to 2965 kPa
    (350 to 430 psi)
  6. If the air outlet temperature fails to meet the specifications in the A/C Performance Temperature and Pressure chart, or if the A/C compressor discharge pressure is high, see the A/C System Diagnosis table below.
A/C SYSTEM DIAGNOSIS

Condition Possible Causes Correction
Rapid A/C clutch cycling (ten or more cycles per minute)

1. Low refrigerant system charge

1. Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.

Refer to REFRIGERANT SYSTEM LEAKS .
Equal pressures, but the A/C clutch does not engage

1. No refrigerant in the refrigerant system

1. Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.

Refer to REFRIGERANT SYSTEM LEAKS .
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2. Open fuse

2. See Wiring Information. Check the fuses. Repair the shorted circuit or component and replace the fuses as required.

Refer to SYSTEM WIRING DIAGRAMS .
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3. Inoperative A/C clutch

3. Test the A/C clutch coil and replace as required.

Refer to COMPRESSOR, A/C .
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4. Improperly installed or inoperative A/C pressure transducer

4. Test the A/C pressure transducer and tighten or replace as required.

Refer to TRANSDUCER, A/C Pressure .
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5. Inoperative evaporator temperature sensor

5. Test the evaporator temperature sensor and replace as required.

Refer to SENSOR, Evaporator Temperature .
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6. Inoperative Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application

6. See DTC Based Diagnostics. Test the PCM or ECM and replace as required.

For Gas, see DIAGNOSTIC CODE INDEX .
Normal pressures, but A/C Performance Test air temperatures at center panel outlet are too high

1. Excessive refrigerant oil in system

1. Recover the refrigerant from the refrigerant system and inspect the refrigerant oil content. Restore the refrigerant oil to the proper level as required.

Refer to OIL, Refrigerant .
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2. Blend door actuator improperly installed or inoperative

2. See Blend Door Actuator. Inspect the actuator for proper operation and replace as required.

Refer to Controls .
-

3. Blend-air door inoperative or sealing improperly

3. Inspect the blend-air door for proper operation and sealing and correct as required.

Refer to HOUSING, HVAC .
The low side pressure is normal or slightly low, and the high side pressure is too low

1. Low refrigerant system charge

1. Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.

Refer to REFRIGERANT SYSTEM LEAKS .
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2. Refrigerant flow through the A/C accumulator is restricted

2. See A/C Accumulator. Replace the restricted accumulator as required.
-

3. Refrigerant flow through the A/C evaporator is restricted

3. Replace the restricted A/C evaporator as required.

Refer to HOUSING-HVAC .
-

4. Inoperative A/C compressor

4. Replace the A/C compressor as required.

Refer to COMPRESSOR, A/C .
The low side pressure is normal or slightly high, and the high side pressure is too high

1. A/C Condenser air flow restricted

1. Check the A/C condenser for damaged fins, foreign objects obstructing air flow through the condenser fins, and missing or improperly installed air seals. Clean, repair, or replace components as required.

Refer to CONDENSER, A/C .
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2. Inoperative radiator cooling fan

2. Test the radiator cooling fan and replace as required.

Refer to COOLING .
-

3. Refrigerant system overcharged

3. See Refrigerant System Charge Level in this group. Recover the refrigerant from the refrigerant system. Charge the refrigerant system to the proper level as required.
-

4. Air in the refrigerant system

4. See REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.
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5. Engine overheating

5. Test the engine cooling system and repair, if required.

Refer to COOLING .
The low side pressure is too high, and the high side pressure is too low

1. Accessory drive belt slipping

1. Inspect the accessory drive belt condition and tension. Replace the accessory drive belt and/or tensioner as required.

Refer to COOLING .
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2. Inoperative A/C expansion valve

2. Test the expansion valve and replace as required.

Refer to VALVE, A/C Expansion .
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3. Inoperative A/C compressor

3. Replace the A/C compressor as required.

Refer to COMPRESSOR, A/C .
The low side pressure is too low, and the high side pressure is too high

1. Restricted refrigerant flow through the refrigerant lines

1. Inspect the refrigerant lines for kinks, tight bends or improper routing. Correct the routing or replace the refrigerant line as required.

See appropriate Liquid, Suction and A/C Discharge Lines. See PLUMBING .
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2. Restricted refrigerant flow through the A/C expansion valve

2. Test the expansion valve and replace as required.

Refer to VALVE, A/C Expansion .
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3. Restricted refrigerant flow through the A/C condenser

3. Replace the restricted condenser as required.

Refer to CONDENSER, A/C .
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