A/C Performance Test

WARNING:

Review the warnings and cautions for this system before performing the procedure. Failure to follow these instructions may result in serious injury or death.

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 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.

Check for Diagnostic Trouble Codes (DTCs) using a scan tool. If no DTCs are found in the A/C heater control, Totally Integrated Power Module (TIPM) or Powertrain Control Module (PCM), go to step 2. If any DTCs are found, repair as required (refer to the DTC INDEX article), then proceed to step 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 13° C (55° F) for this test as well. Place the vehicle in the testing area until the temperature within the vehicle reaches a minimum of 21° C (70° F) prior to conducting the A/C Performance Test.
Operate the heating and A/C system under the following conditions.
- Engine at idle and operating temperature
- Doors 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, high blower 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 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 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 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 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	6 -15° C (42 - 59° F)	7 -18° C (45 - 64° F)	9 - 21° C (48 - 69° F)	11 - 22° C (52 - 72° F)	13 - 24° C (56 - 75° F)
A/C High Side Pressure	1034 - 1896 kPa (150 - 275 psi)	1207 - 2068 kPa (175 - 300 psi)	1379 - 2241 kPa (200 - 325 psi)	1551 - 2413 kPa (225 - 350 psi)	1724 - 2241 kPa (250 - 375 psi)
A/C Low Side Pressure	214 - 365 kPa (31 - 53 psi)	248 - 407 kPa (36 - 59 psi)	283 - 476 kPa (41 - 69 psi)	317 - 483 kPa (46 - 70 psi)	359 - 496 kPa (52 - 72 psi)

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.

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. See Refrigerant System Leaks in this group. Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as 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 group. Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.
	2. Open fuse	2. See 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	3. See A/C Compressor in this group. Test the A/C clutch coil and replace as required.
	4. Improperly installed or inoperative A/C pressure transducer	4. See A/C Pressure Transducer in this group. Test the transducer and replace as required.
	5. Improperly installed or inoperative evaporator temperature sensor	5. See Evaporator Temperature Sensor in this group. Correctly install or test and replace the sensor as required.
	6. Inoperative A/C heater control, TIPM or PCM	6. See Group 28 - DTC Based Diagnostics. Test the A/C heater control, TIPM and PCM. Replace as required.
Normal refrigerant 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 group. 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 actuator inoperative	2. See Blend Door Actuator this group. Test for proper operation. Replace as required.
	3. Blend door inoperative or sealing improperly	3. See HVAC Housing in this group. Inspect the blend door for proper operation and sealing. Repair as 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 group. 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. See A/C Evaporator in this group. Replace the restricted A/C evaporator as required.
	3. Inoperative A/C compressor	3. See A/C Compressor in this group. Replace the compressor as 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 group. 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 group. Replace the restricted A/C receiver/drier as required.
	3. Inoperative radiator cooling fan	3. See Group 7 - Cooling. Test the radiator cooling fan and replace as required.
	4. Refrigerant system overcharged	4. See Refrigerant System Charge in this group. Recover the refrigerant from the refrigerant system. Charge the refrigerant system to the proper level as required.
	5. Air in the refrigerant system	5. See Refrigerant System Leaks in this group. Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required.
	6. Engine overheating	6. See Group 7 - Cooling. Test the engine cooling system and repair as required.
The low side pressure is too high, and the high side pressure is too low	1. Accessory drive belt slipping	1. See Group 7 - Cooling. Inspect the accessory drive belt condition and tension. Replace the accessory drive belt or tensioner as required.
	2. Inoperative A/C expansion valve	2. See A/C Expansion Valve in this group. Test and replace the valve as required.
	3. Inoperative A/C compressor	3. See A/C Compressor in this group. Replace the A/C compressor as 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 A/C Liquid Line, Suction Line and Discharge Line in this group. Inspect the refrigerant lines for kinks, tight bends or improper routing. Correct the routing or replace the refrigerant line as required.
	2. Restricted refrigerant flow through the A/C expansion valve	2. See A/C Expansion Valve in this group. Test and replace the valve as required.
	3. Restricted refrigerant flow through the A/C condenser	3. See A/C Condenser in this group. Replace the restricted A/C condenser as required.