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A/C Performance Test

WARNING: This page is about a different car, the 2012 RAM Pickup and 2012 RAM Cab & Chassis. 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. Refer to PLUMBING, WARNING  and PLUMBING, CAUTION . Failure to follow the warnings and cautions may result in 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 takes up to 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 A/C system 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.

NOTE:

The work area ambient temperature must be above 21° C (70° F) and the evaporator temperature must be above 13° C (55° F) prior to conducting the A/C Performance Test.

  1. Conduct the A/C System Performance Test (Cooldown Test) found within the HVAC System Test. Refer to appropriate Electrical Diagnostic article. . If no Diagnostic Trouble Codes (DTCs) are found in the A/C-heater control, Totally Integrated Power Module (TIPM), 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, refer to  2.
  2. Connect a tachometer and a manifold gauge set or an A/C recycling/charging station.
  3. Operate the heating-A/C system under the following conditions.
    • Engine at 1, 000 rpm at operating temperature
    • Door and windows closed
    • 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 .
  4. Insert a thermometer in the driver side center panel air outlet and operate the A/C system until the thermometer temperature stabilizes.
    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 temperature ("feels like" temperature), when the 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 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 (coldest temperature).
    A/C PERFORMANCE TEMPERATURE AND PRESSURE

    Ambient Air Temperature (Apparent)  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)
    Compressor Discharge 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. Refer to A/C SYSTEM DIAGNOSIS  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.
A/C SYSTEM DIAGNOSIS

Condition  Possible Causes  Correction 
Constant A/C compressor engagement and warm air from passenger vents 1. Low refrigerant system charge 1. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.
Equal A/C system pressures, but the A/C clutch does not engage 1. No refrigerant in the refrigerant system 1. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.
  2. Open fuse 2. Refer to appropriate Wiring Information. Check the fuse in the junction block. Repair the shorted circuit or component and replace the fuse as required.
  3. Inoperative A/C clutch coil 3. Refer to COMPRESSOR, A/C . Test the A/C clutch coil and replace as required.
  4. Improperly installed or inoperative Evaporator Temperature Sensor 4. Refer to SENSOR, EVAPORATOR TEMPERATURE . Correctly install or test and replace the sensor as required.
  5. Improperly installed or inoperative A/C pressure transducer 5. Refer to TRANSDUCER, A/C PRESSURE . Correctly install or test and replace the sensor as required.
  6. Inoperative A/C-heater control, TIPM or PCM/ECM 6. Refer to the appropriate Electrical Diagnostic Procedures for testing of the A/C-heater control, TIPM or PCM/ECM. Test the module and replace as required.
Normal A/C system pressures, but A/C Performance Test air temperatures at center panel outlet are too high 1. Excessive refrigerant oil in system 1. Refer to OIL, REFRIGERANT . Recover the refrigerant from the refrigerant system and inspect the refrigerant oil content. Restore the refrigerant oil to the proper level as required.
  2. Blend door inoperative or sealing improperly 2. Refer to ACTUATOR, BLEND DOOR . Inspect the blend door for proper operation and sealing and correct as required.
  3. Blend door actuator inoperative 3. Refer to ACTUATOR, BLEND DOOR . Refer to the appropriate Electrical Diagnostic Procedures for blend door actuator diagnosis. Repair or replace as required.
The low side A/C system pressure is normal or slightly low, and the high side A/C system pressure is too low 1. Low refrigerant system charge 1. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.
  2. Refrigerant flow through the A/C evaporator is restricted 2. Refer to EVAPORATOR, A/C . Replace the restricted evaporator as required.
  3. Inoperative A/C compressor 3. Refer to COMPRESSOR, A/C . Replace the A/C compressor as required.
The low side A/C system pressure is normal or slightly high, and the high side A/C system pressure is too high 1. A/C Condenser air flow restricted 1. Refer to CONDENSER, A/C . 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.
  2. Refrigerant flow through the A/C receiver/drier is restricted 2. Refer to DRIER, A/C RECEIVER . Replace the restricted A/C receiver/drier as required.
  3. Inoperative cooling fan 3. Refer to DIAGNOSIS AND TESTING . Test the cooling fan and replace as required.
  4. Refrigerant system overcharged 4. Refer to REFRIGERANT SYSTEM CHARGE . Recover the refrigerant from the refrigerant system. Charge the refrigerant system to the proper level as required.
  5. Air in the refrigerant system 5. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.
  6. Engine overheating 6. Refer to ENGINE COOLING SYSTEM OVERHEATING . Test the cooling system and repair as required.
The low side A/C system pressure is too high, and the high side A/C system pressure is too low 1. Accessory drive belt slipping 1. Refer to ACCESSORY DRIVE . Inspect the accessory drive belt condition and tension. Tighten or replace the accessory drive belt as required.
  2. Inoperative A/C expansion valve 2. Refer to VALVE, A/C EXPANSION . Test and replace the valve as required.
  3. Inoperative A/C compressor 3. Refer to COMPRESSOR, A/C . Replace the A/C compressor as required.
The low side A/C system pressure is too low, and the high side A/C system pressure is too high 1. Restricted refrigerant flow through the refrigerant lines 1. Refer to LINE, A/C LIQUID  and LINE, A/C SUCTION  and LINE, A/C DISCHARGE . Inspect the refrigerant lines for kinks, tight bends or improper routing. Correct the routing or replace the refrigerant line as required.
  2. Inoperative A/C expansion valve 2. Refer to VALVE, A/C EXPANSION . Test and replace the valve as required.
  3. Restricted refrigerant flow through the A/C condenser 3. Refer to CONDENSER, A/C . Replace the restricted A/C condenser as required.
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