A/C COOL DOWN TEST
The A/C-heater control module can perform an A/C cool down test, which is a test performed during the manufacturing process to confirm that the air conditioning system is performing satisfactorily. This test can also provide a quick confirmation of air conditioning system performance to the service technician. If the test is completed satisfactorily, no further service is required. If the test is failed, proceed to the A/C PERFORMANCE TEST to confirm the A/C system is operating properly, or use a DRBIII® scan tool to diagnose the A/C system control and distribution systems. Refer to BODY DIAGNOSTIC PROCEDURES for more information.
A/C PERFORMANCE TEST
The A/C system is designed to provide the passenger compartment with low temperature and low humidity air. The A/C evaporator, located in the HVAC housing is cooled to temperatures near the freezing point. As warm damp air passes over the fins of the A/C evaporator, the air transfers its heat to the refrigerant in the evaporator coils and the moisture in the air condenses on the evaporator fins. During periods of high heat and humidity, an A/C system will be more effective in the Recirculation mode (max-A/C). With the system in the Recirculation mode, only air from the passenger compartment passes through the A/C evaporator. As the passenger compartment air dehumidifies, the A/C system performance levels rise.
Humidity has an important bearing on the temperature of the air delivered to the interior of the vehicle. It is important to understand the effect that humidity has on the performance of the A/C system. When humidity is high, the A/C evaporator has to perform a double duty. It must lower the air temperature, and it must lower the temperature of the moisture in the air that condenses on the evaporator fins. Condensing the moisture in the air transfers heat energy into the evaporator fins and coils. This reduces the amount of heat the A/C evaporator can absorb from the air. High humidity greatly reduces the ability of the A/C evaporator to lower the temperature of the air.
However, evaporator capacity used to reduce the amount of moisture in the air is not wasted. Wringing some of the moisture out of the air entering the vehicle adds to the comfort of the passengers. Although, an owner may expect too much from their A/C system on humid days. A performance test is the best way to determine whether the system is performing up to design standards. This test also provides valuable clues as to the possible cause of trouble with the A/C system. The ambient air temperature in the location where the vehicle will be tested must be a minimum of 21° C (70° F) for this test.
PERFORMANCE TEST PROCEDURE
| WARNING | Refer to the applicable warnings and cautions for this system before performing the following operation (Refer to HEATING & AIR CONDITIONING/PLUMBING - WARNINGS) and (Refer to HEATING & AIR CONDITIONING/PLUMBING - CAUTIONS) . Failure to follow the warnings and cautions could result in possible personal injury or death. |
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.
- Connect a tachometer to monitor the engine speed.
- Remove the caps from the refrigerant system service ports and attach a manifold gauge set to monitor the refrigerant system pressures.
- Set the A/C-heater control so that the compressor is engaged, the air within the vehicle is being recirculated, the output air is directed through the panel outlets, the temperature control is in the full cool position or the ATC temperature set points are set to LO, and the blower motor is operating at its highest speed.
- Start the engine and allow the engine to operate for about five minutes or until it reaches normal operating temperature. Then hold the engine speed at 1000 RPM with the compressor clutch engaged. If the compressor clutch does not engage, proceed with diagnosis of the compressor clutch coil «(Refer to HEATING & AIR CONDITIONING/CONTROLS - FRONT/A/C COMPRESSOR CLUTCH/COIL - DIAGNOSIS AND TESTING»(ref-245452-S24570927152006110200000) .
- Close all the vehicle windows and doors.
- Insert a thermometer in the left center panel outlet and operate the engine for five minutes.
- With the compressor clutch engaged, record the left center panel air outlet discharge temperature, the discharge pressure (high side service port) and the suction pressure (low side service port). The compressor clutch may cycle, depending upon the ambient temperature and humidity. If the clutch cycles, use the readings obtained before the clutch disengaged.
- Compare the air temperature at the center panel air outlet and the A/C compressor discharge pressure (high side) to the «A/C PERFORMANCE TEMPERATURE AND PRESSURE»(ref-245452-S18344082842006110200000) chart. A/C PERFORMANCE TEMPERATURE AND PRESSURE Ambient Temperature 21° C (70° F) 27° C (80° F) 32° C (90° F) 38° C (100° F) 43° C (110° F) Left Center Panel Outlet Discharge Air Temperature 1 to 8° C (34 to 46° F) 3 to 9° C (37 to 49° F) 4 to 10°C (39 to 50° F) 6 to 11°C (43 to 52° F) 7 to 18° C (45 to 65° F) Discharge Pressure (High Side Service Port) 1034 to 1724 kPa (150 to 250 psi) 1517 to 2275 kPa (220 to 330 psi) 1999 to 2620 kPa (290 to 380 psi) 2068 to 2965 kPa (300 to 430 psi) 2275 to 3421 kPa (330 to 450 psi) Suction Pressure (Low Side Service Port) 103 to 207 kPa (15 to 30 psi) 117 to 221 kPa (17 to 32 psi) 138 to 241 kPa (20 to 35 psi) 172 to 269 kPa (25 to 39 psi) 207 to 345 kPa (30 to 50 psi)
- If the air outlet temperature fails to meet the specifications in the «A/C PERFORMANCE TEMPERATURE AND PRESSURE»(ref-245452-S18344082842006110200000) , or if the A/C compressor discharge pressure is high, refer to the «A/C PRESSURE DIAGNOSIS»(ref-245452-S20953650342006110200000) chart.
| Condition | Possible Causes | Correction |
|---|---|---|
| Constant compressor engagement and warm air from passenger vents. | 1. Low refrigerant system charge. | 1. See REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. |
| Equal pressures, but the compressor clutch does not engage. | 1. No refrigerant in the refrigerant system. | 1. See REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. |
| 2. Faulty fuse. | 2. Check the fuses in the integrated power module (IPM). Repair the shorted circuit or component and replace the fuses, if required. | |
| 3. Faulty A/C compressor clutch coil. | 3. See A/C COMPRESSOR CLUTCH COIL . Test the compressor clutch coil and replace, if required. | |
| 4. Faulty A/C compressor clutch relay. | 4. See A/C COMPRESSOR CLUTCH RELAY . Test the compressor clutch relay and relay circuits. Repair the circuits or replace the relay, if required. | |
| 5. Improperly installed or faulty Evaporator Temperature Sensor. | 5. See EVAPORATOR TEMPERATURE SENSOR . Reinstall or replace the sensor as required. | |
| 6. Faulty A/C pressure transducer. | 6. See A/C PRESSURE TRANSDUCER . Test the switch and replace, if required. | |
| 7. Faulty Powertrain Control Module (PCM). | 7. Test the PCM and replace, if required. | |
| 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 . 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-air door inoperative or sealing improperly. | 2. See HVAC HOUSING . Inspect the blend-air door for proper operation and sealing and correct, if required. | |
| 3. Blend door actuator faulty or inoperative. | 3. Perform blend door actuator diagnosis, replace if faulty. | |
| 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 . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. |
| 2. Refrigerant flow through the receiver/drier is restricted. | 2. See RECEIVER/DRIER . Replace the restricted receiver/drier, if required. | |
| 3. Refrigerant flow through the evaporator coil is restricted. | 3. See A/C EVAPORATOR . Replace the restricted evaporator coil, if required. | |
| 4. Faulty compressor. | 4. See A/C COMPRESSOR . Replace the compressor, if required. | |
| The low side pressure is normal or slightly high, and the high side pressure is too high. | 1. 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. Refer to COOLING for more information on air seals. Clean, repair, or replace components as required. |
| 2. Inoperative cooling fan. | 2. Refer to COOLING for more information. Test the cooling fan and replace, if required. | |
| 3. Refrigerant system overcharged. | 3. See REFRIGERANT SYSTEM CHARGE . Recover the refrigerant from the refrigerant system. Charge the refrigerant system to the proper level, if 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, if required. | |
| 5. Engine overheating. | 5. Refer to COOLING for more information. Test the 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. Refer to COOLING for more information. Inspect the accessory drive belt condition and tension. Tighten or replace the accessory drive belt, if required. |
| 2. Faulty expansion valve. | 2. See EXPANSION VALVE . Replace the expansion valve, if required. | |
| 3. Faulty compressor. | 3. See A/C COMPRESSOR . Replace the 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 A/C DISCHARGE LINE . Inspect the refrigerant lines for kinks, tight bends or improper routing. Correct the routing or replace the refrigerant line, if required. |
| 2. Restricted refrigerant flow through the expansion valve. | 2. See EXPANSION VALVE . Replace the expansion valve, if required. | |
| 3. Restricted refrigerant flow through the condenser. | 3. See A/C CONDENSER . Replace the restricted condenser, if required. |
A/C PRESSURE DIAGNOSIS
HEATER PERFORMANCE TEST
| WARNING | Review safety precautions and warnings before performing this procedure. (Refer to HEATING & AIR CONDITIONING/PLUMBING - WARNINGS) and (Refer to HEATING & AIR CONDITIONING/PLUMBING - CAUTIONS) . Failure to follow the warnings and cautions could result in possible personal injury or death. |
Check the coolant level, drive belt tension, radiator air flow and fan operation. Start engine and allow to warm up to normal operating temperature.
| WARNING | Do not remove radiator cap when engine is hot, personal injury can result. |
If vehicle has been run recently, wait 15 minutes before removing the radiator cap. Place a rag over the cap and turn it to the first safety stop. Allow pressure to escape through the overflow tube. When the system pressure stabilizes, remove the cap completely.
MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system by two heater hoses. With the engine idling at normal operating temperature, set the temperature control to maximum heat, the mode control to the floor position, and the blower in the highest speed position. Using a test thermometer, check the temperature of the air being discharged from the floor outlets. Compare the test thermometer reading to the HEATER TEMPERATURE REFERENCE chart.
| Ambient Temperature | Minimum Floor Outlet Temperature | ||
|---|---|---|---|
| Celsius | Fahrenheit | Celsius | Fahrenheit |
| 15.5° | 60° | 62.2° | 144° |
| 21.1° | 70° | 63.8° | 147° |
| 26.6° | 80° | 65.5° | 150° |
| 32.2° | 90° | 67.2° | 153° |
HEATER TEMPERATURE REFERENCE
If the floor outlet air temperature is insufficient, check that the cooling system is operating to specifications (Refer to COOLING/ENGINE - DIAGNOSIS AND TESTING) . Both heater hoses should be HOT to the touch (the coolant return hose should be slightly cooler than the supply hose). If the coolant return hose is much cooler than the supply hose, locate and repair the engine coolant flow obstruction in heater system.
A/C CLUTCH INSPECTION
Note. The A/C clutch can be serviced in the vehicle. The refrigerant system can remain fully-charged during compressor clutch, pulley and bearing assembly, or coil replacement.
Examine the friction surfaces of the clutch pulley and the clutch plate for wear. (Scheme 21) The pulley and plate should be replaced if there is excessive wear or scoring.
If the friction surfaces are oily, inspect the shaft and nose area of the A/C compressor for refrigerant oil. If refrigerant oil is found, the compressor shaft seal is leaking and the A/C compressor must be replaced.
Check the clutch pulley bearing for roughness or excessive leakage of grease. Replace the pulley and bearing assembly, if required.
Scheme 21
| 1 - A/C COMPRESSOR SHAFT |
|---|
| 2 - CLUTCH PLATE |
| 3 - SHIM |