A/C COOL DOWN TEST
The heater-A/C 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 the appropriate diagnostic information.
A/C PERFORMANCE TEST
The A/C system is designed to remove heat and humidity from the air entering the passenger compartment. The evaporator, located in the HVAC housing, is cooled to temperatures near the freezing point. As warm damp air passes over the fins in the A/C evaporator, moisture in the air condenses to water, dehumidifying the air. Condensation on the evaporator fins reduces the evaporators ability to absorb heat. During periods of high heat and humidity, an A/C system will be less effective. With the instrument control set to recirculation mode, only air from the passenger compartment passes through the A/C evaporator. As the passenger compartment air dehumidifies, A/C 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 tubing. 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 - FRONT - WARNINGS) and (Refer to HEATING & AIR CONDITIONING/PLUMBING - FRONT - 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 and a manifold gauge set.
- Set the mode control to the Recirculation Mode position, the temperature control to the full cool position and the blower to the highest speed position.
- Start the engine and hold at 1,000 rpm with the A/C compressor clutch engaged.
- The engine should be warmed up to operating temperature with the doors closed and windows open.
- Insert a thermometer in the driver's side center panel A/C-heater outlet and operate the engine for five minutes.
- If the compressor clutch does not engage, proceed with diagnosis of the compressor clutch coil. (Refer to «A/C COMPRESSOR CLUTCH COIL»(ref-248916-S04320168092007022700000) ).
- With the A/C compressor clutch engaged, compare the air temperature at the center panel outlet and the compressor discharge pressure to the A/C Performance Temperature and Pressure chart. The compressor clutch may cycle, depending upon the ambient temperature and humidity. If the clutch cycles, use the readings obtained before the clutch disengaged. 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 «A/C PERFORMANCE TEMPERATURE AND PRESSURE»(ref-248916-S08683896382007022700000) , or if the compressor discharge pressure is high, refer to «A/C PRESSURE DIAGNOSIS»(ref-248916-S06623012152007022700000) .
| Condition | Possible Causes | Correction |
|---|---|---|
| Rapid A/C compressor clutch cycling (ten or more cycles per minute). | 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. Repair the shorted circuit or component and replace the fuses, if required. Refer to appropriate service information. | |
| 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 . Test the sensor and replace, if required. | |
| 6. Faulty A/C pressure transducer. | 6. See A/C Pressure Transducer in this service information. Test the sensor and replace, if required. | |
| 7. Faulty Powertrain Control Module (PCM). | 7. Refer to POWERTRAIN DIAGNOSTIC PROCEDURES for testing of the PCM. 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 door actuator improperly installed or faulty. | 2. See BLEND DOOR ACTUATOR . Inspect the actuator for proper operation and replace, if required. | |
| 3. Blend door inoperative or sealing improperly. | 3. See HVAC HOUSING . Inspect the blend door for proper operation and sealing. Repair if required. | |
| 4. Blend door not in full cold position. | Use a DRBIII Scan Tool to check for DTCs and blend door position. Refer to BODY DIAGNOSTIC PROCEDURES . | |
| 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 A/C evaporator is restricted. | 2. See A/C EVAPORATOR . Replace the restricted A/C evaporator, if required. | |
| 3. Faulty A/C compressor. | 3. See A/C Compressor in this article. 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. 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 receiver/drier is restricted. | 2. See RECEIVER / DRIER . Replace the restricted receiver/drier, if required. | |
| 3. Inoperative radiator cooling fan. | 3. Test the radiator cooling fan and replace, if required. Refer to COOLING . | |
| 4. Refrigerant system overcharged. | 4. See REFRIGERANT SYSTEM CHARGE . 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 . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required. | |
| 6. Engine overheating. | 6. 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. Tighten or replace the accessory drive belt, if required. Refer to COOLING . |
| 2. Faulty A/C expansion valve. | 2. See EXPANSION VALVE . Replace the valve, if required. | |
| 3. Faulty A/C compressor. | 3. See A/C Compressor in this article. 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 A/C expansion valve. | 2. See EXPANSION VALVE . Replace the valve, if required. | |
| 3. Restricted refrigerant flow through the A/C 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 - FRONT - WARNINGS) and (Refer to HEATING & AIR CONDITIONING/PLUMBING - FRONT - 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 TEMPERATURE REFERENCE .
| 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° |
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 27) 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 27
| 1 - A/C COMPRESSOR SHAFT |
|---|
| 2 - CLUTCH PLATE |
| 3 - SHIM |
SYSTEM CHARGE LEVEL TEST
| WARNING | Refer to the warnings and cautions for this system before performing the following operation (Refer to HEATING & AIR CONDITIONING/PLUMBING - FRONT - WARNINGS) and (Refer to HEATING & AIR CONDITIONING/PLUMBING - FRONT - CAUTIONS) . Failure to follow the warnings and cautions could result in possible personal injury or death. |
Note. Always refer to the underhood HVAC Specification Label for the refrigerant fill capacity of the vehicle being serviced.
The procedure that follows should be used to determine whether the refrigerant system contains the proper refrigerant charge. Symptoms of an improper refrigerant charge (low) include: poor air conditioner performance, fog emitted from the air conditioner outlets, a hissing sound from the expansion valve/evaporator area. There are two different methods with which the refrigerant charge level may be tested
- Using a DRBIII® scan tool, a thermocouple and the Charge Determination Chart. (Scheme 28) Refer to the appropriate diagnostic information.
- Using a manifold gauge set, a thermocouple and the Charge Determination Chart. (Scheme 28)
A temperature probe is required to measure liquid line temperature. The clamp-on, Type K thermocouple temperature probe used in this procedure is available through the DaimlerChrysler Professional Service Equipment (PSE) program. This probe (PSE #66-324-0014 or #80PK-1A) is compatible with temperature-measuring instruments that accept Type K thermocouples, and have a miniature connector input. Other temperature probes are available through aftermarket sources; however, all references in this procedure will reflect the use of the probe made available through the PSE program.
In order to use the temperature probe, a digital thermometer will also be required. If a digital thermometer is not available, an adapter is available through the PSE program that will convert any standard digital multimeter into a digital thermometer. This adapter is designed to accept any standard Type K thermocouple. If a digital multimeter is not available, this tool is also available through the PSE program.
Note. When connecting the service equipment couplings to the refrigerant system service ports, be certain that the valve of each coupling is fully closed. This will reduce the amount of effort required to make the connection.
Scheme 28
- Remove the caps from the refrigerant system service ports and attach a manifold gauge set or a R-134a refrigerant recovery/recycling/charging station that meets SAE Standard J2210 to the refrigerant system.
- Attach a clamp-on thermocouple to the liquid line. The thermocouple must be placed as close to the A/C pressure transducer as possible to accurately observe liquid line temperature.
- Bring the refrigerant system up to operating temperature and pressure. This is done by allowing the engine to run at idle under the following conditions for five minutes. Front windows are open. Transaxle in Park. Front heater-A/C controls set to outside air, full cool, panel mode, blower high, and compressor engaged. If the vehicle is so equipped, the rear heater-A/C controls must be set to full cool and blower high.
- Raise the liquid line (discharge) pressure to about 1793 kPa (260 psi) by placing a piece of cardboard over part of the front side of the condenser. To place the cardboard properly, remove the upper radiator sight shield from the front fascia. Cover only enough of the condenser to raise and maintain the liquid line pressure at the specified level.
- Observe the liquid line (discharge) pressure and liquid line temperature. Using the Charge Determination Chart, determine whether the refrigerant system is operating within the Proper Charge Range. (Scheme 28) If the refrigerant system is operating in the Undercharged area of the chart, add 0.057 kilogram (0.125 pound or 2 ounces) of refrigerant to the system. If the refrigerant system is operating in the Overcharged area of the chart, reclaim 0.057 kilogram (0.125 pound or 2 ounces) of refrigerant from the system.
- Recheck the system charge level following each refrigerant adjustment. Continue this process until the system readings are in the Proper Charge Range area on the Charge Determination Chart.