A/C Performance Test
Review the warnings and cautions for this system before performing the procedure. Failure to follow these instructions may result in serious or fatal injury.
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.
The ambient air temperature of the location where the vehicle will be tested must be a minimum of 21°C (70°F). Also the A/C evaporator temperature must be a minimum of 18°C (65°F) prior to conducting the A/C Performance Test.
- Use a scan tool to observe the engine rpm and connect a manifold gauge set or an A/C recycling/charging station.
- Operate the HVAC 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 application).
- A/C heater controls set to Recirculation mode (MAX-A/C), full cool, panel mode, blower set to high and with A/C compressor engaged. If the A/C compressor does not engage, see the A/C System Diagnosis table.
- Insert a thermometer in the driver side center panel air outlet and operate the A/C system until the thermometer temperature stabilizes or a minimum of 5 minutes.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.
- With the A/C clutch engaged, compare the air temperature at the center panel outlet and the 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)Maximum Allowable Air Temperature at Center Panel Outlet 9°C
(48°F)9°C
(48°F)12°C
(54°F)15°C
(59°F)18°C
(65°F)Suction Pressure at Service Port (Low Side) 138 to 310 kPa
(20 to 45 psi)138 to 345 kPa
(20 to 50 psi)207 to 365 kPa
(30 to 55 psi)207 to 414 kPa
(30 to 60 psi)241 to 448 kPa
(35 to 65 psi)Discharge Pressure at Service Port (High Side) 1034 to 1724 kPa
(150 to 250 psi)1379 to 2068 kPa
(200 to 300 psi)1551 to 2241 kPa
(225 to 325 psi)1724 to 2413 kPa
(250 to 350 psi)2068 to 2758 kPa
(300 to 400 psi) - If the air outlet temperature fails to meet the specifications in the A/C Performance Temperature and Pressure chart, or if the compressor discharge pressure is high, see the A/C System Diagnosis table.
| CONDITION | POSSIBLE CAUSES | CORRECTION |
|---|---|---|
| FOR APPLICATIONS WITH A FIXED DISPLACEMENT COMPRESSOR, RAPID A/C CLUTCH CYCLING WITH POOR PANEL OUTLET TEMPERATURES | 1. Low refrigerant system charge | 1. See Refrigerant System Leaks in this service information. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. |
| EQUAL PRESSURES, BUT THE A/C CLUTCH DOES NOT ENGAGE | 1. No refrigerant in the refrigerant system | 1. See Refrigerant System Leaks in this service information. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. |
| 2. Open fuse | 2. See Wiring Information. Check the fuses in the Body Control Module. Repair the shorted circuit or component and replace the fuses. | |
| 3. Inoperative A/C clutch coil | 3. See A/C Compressor in this service information. Test the A/C clutch coil and replace, if required. | |
| 4. Inoperative A/C clutch relay | 4. See A/C Clutch Relay in this service information. Test the A/C clutch relay and relay circuits. Repair the circuits or replace the relay, if required. | |
| 5. Improperly installed or inoperative evaporator temperature sensor | 5. See Evaporator Temperature Sensor in this service information. Test the sensor and replace, if required. | |
| 6. Inoperative A/C pressure transducer | 6. See A/C Pressure Transducer in this service information. Test the sensor and replace, if required. | |
| 7. Inoperative Powertrain Control Module (PCM) | 7. See service information. Test the PCM and replace, if required. | |
| 8. Inoperative HVAC module | 8. See service information. Test the HVAC module and replace, if required. | |
| 9. Inoperative A/C heater control | 9. Test the A/C heater control and circuits for compressor clutch engagement signal. Repair as necessary. | |
| NORMAL PRESSURES, BUT A/C PERFORMANCE TEST AIR TEMPERATURES AT CENTER PANEL OUTLET ARE TOO HIGH | 1. Excessive refrigerant oil in system | 1. See Refrigerant Oil Level in this service information. Recover the refrigerant from the refrigerant system and inspect the refrigerant oil content. Restore the refrigerant oil to the proper level, if required. |
| 2. Blend door actuator or cable inoperative or improperly installed | 2. See Blend Door Actuator or Cable in this service information. Inspect for proper operation and replace, if required. | |
| 3. Blend door(s) inoperative or sealing improperly | 3. See HVAC Housing in this service information. Inspect each blend door for proper operation and sealing. Repair if required. | |
| THE LOW SIDE PRESSURE IS NORMAL OR SLIGHTLY LOW, AND THE HIGH SIDE PRESSURE IS TOO LOW | 1. Low refrigerant system charge | 1. See Refrigerant System Leaks in this service information. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. |
| 2. Refrigerant flow through the A/C evaporator is restricted | 2. See A/C Evaporator in this service information. Replace the restricted A/C evaporator, if required. | |
| 3. Restricted suction line | 3. See A/C Suction line in this service information. Check the suction line for restriction. Replace the suction line, if required. | |
| 4. Inoperative A/C compressor | 4. See A/C Compressor in this service information. Replace the compressor, if required. | |
| 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. See A/C Condenser in this service information. 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. See A/C Receiver/Drier in this service information. Replace the restricted A/C receiver/drier, if required. | |
| 3. Inoperative radiator cooling fan | 3. See service information. Test the radiator cooling fan and replace, if required. | |
| 4. Refrigerant system overcharged | 4. See Refrigerant System Charge in this service information. Recover the refrigerant from the refrigerant system. Charge the refrigerant system to the proper level, if required. | |
| 5. Air in the refrigerant system | 5. See Refrigerant System Leaks in this service information. Refer to DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. | |
| 6. Engine overheating | 6. See service information. Test the engine cooling system and repair, if required. | |
| THE LOW SIDE PRESSURE IS TOO HIGH, AND THE HIGH SIDE PRESSURE IS TOO LOW | 1. Accessory drive belt slipping | 1. See service information. Inspect the accessory drive belt condition and tension. Tighten or replace the accessory drive belt, if required. |
| 2. Restricted suction line | 2. See A/C Suction line in this service information. Check the suction line for restriction. Replace the suction line, if required. | |
| 3. Inoperative A/C expansion valve | 3. See A/C Expansion Valve in this service information. Replace the A/C expansion valve, if required. | |
| 4. Inoperative A/C compressor | 4. See A/C Compressor in this service information. Replace the A/C compressor, if required. | |
| THE LOW SIDE PRESSURE IS TOO LOW, AND THE HIGH SIDE PRESSURE IS TOO HIGH | 1. Restricted refrigerant flow through the refrigerant lines | 1. See Liquid Line, Suction Line and Discharge Line in this service information. Inspect the refrigerant lines for kinks, tight bends or improper routing. Correct the routing or replace the refrigerant lines, as required. |
| 2. Restricted refrigerant flow through the A/C expansion valve | 2. See A/C Expansion Valve in this service information. Replace the A/C expansion valve, if required. | |
| 3. Restricted refrigerant flow through the A/C condenser | 3. See A/C Condenser in this service information. Replace the restricted A/C condenser, if required. |