A/C PERFORMANCE TEST
| WARNING | Refer to the applicable warnings and cautions for this system before performing the following operation. See WARNING and CAUTION . Failure to follow the warnings and cautions could result in possible 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 3 or 4 "reclaim" cycles to remove all of the refrigerant charge. 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 using a scan tool. If no DTCs are found in the powertrain control module (PCM) or engine control module (ECM), depending on engine application, go to step 2 .
- Connect a tachometer and a manifold gauge set or an A/C recycling/charging station.
- Operate the heating-A/C 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 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, see the A/C System Diagnosis chart.
- 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.
- With the A/C compressor 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 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 Air Temperature 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) Condenser Outlet 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)
- 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, refer to «A/C SYSTEM DIAGNOSIS»(ref-306135-S36603365922008120900000) .
| 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 . 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 . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required. |
| 2. Open fuse. | 2. Check the fuses in the power distribution center and the junction block. Repair the shorted circuit or component and replace the fuses as required. | |
| 3. Inoperative A/C clutch field coil. | 3. See CLUTCH-A/C COMPRESSOR . Test the A/C clutch field coil and replace as required. | |
| 4. Inoperative A/C clutch relay. | 4. Test the A/C clutch relay and relay circuits. Repair the circuits or replace the relay as required. | |
| 5. Improperly installed or inoperative A/C pressure transducer. | 5. Test the A/C pressure transducer and tighten or replace as required. | |
| 6. Inoperative evaporator temperature sensor. | 6. Test the evaporator temperature sensor and replace as required. | |
| 7. Inoperative powertrain control module (PCM) or engine control module (ECM), depending on engine application. | 7. Refer to the proper Diagnostic article for testing of the PCM or ECM. Test the PCM or ECM and replace as required. | |
| Normal pressures, but A/C Performance Test air temperatures at center panel outlet are too high. | 1. Excessive refrigerant oil in system. | 1. 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 improperly installed or inoperative. | 2. Inspect the actuator for proper operation and replace as required. See ACTUATOR-BLEND DOOR . | |
| 3. Blend-air door inoperative or sealing improperly. | 3. Inspect the blend-air door for proper operation and sealing and correct 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 . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system as required. |
| 2. Refrigerant flow through the A/C accumulator is restricted. | 2. Replace the restricted accumulator as required. | |
| 3. Refrigerant flow through the A/C evaporator is restricted. | 3. Replace the restricted A/C evaporator as required. | |
| 4. Inoperative A/C compressor. | 4. Replace the A/C 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. 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. Inoperative radiator cooling fan. | 2. Test the radiator cooling fan and replace as required. See COOLING . | |
| 3. Refrigerant system overcharged. | 3. Recover the refrigerant from the refrigerant system. Charge the refrigerant system to the proper level as 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 as required. | |
| 5. Engine overheating. | 5. Test the engine cooling system and repair, if required. See 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. Replace the accessory drive belt and/or tensioner as required. See ACCESSORY DRIVE . |
| 2. Inoperative A/C expansion valve. | 2. Test the expansion valve and replace as required. | |
| 3. Inoperative A/C compressor. | 3. 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. 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. Test the expansion valve and replace as required. | |
| 3. Restricted refrigerant flow through the A/C condenser. | 3. Replace the restricted condenser as required. |
A/C SYSTEM DIAGNOSIS
COIL CURRENT DRAW TEST
- Verify the battery state of charge. Refer to «DIAGNOSIS AND TESTING»(ref-306137-S37965693842008120900000) .
- Connect an ammeter (0 to 10 ampere scale selected) in series with the clutch field coil feed terminal. Connect a voltmeter (0 to 20 volt scale selected) to measure voltage across the battery and the clutch coil.
- With the A/C-heater control in the A/C mode and the blower motor at low speed, start the engine and allow it to run at a normal idle speed.
- The A/C clutch should engage immediately, and the clutch field coil supply voltage should be within two volts of the battery voltage. If the field coil supply voltage is OK, go to step 5 . If the field coil supply voltage is not within two volts of battery voltage, test the clutch field coil feed circuit for excessive voltage drop and repair as necessary.
- Refer to the following A/C Clutch Field Coil Specifications chart for the acceptable A/C clutch field coil current draw. If voltage is more than 12.5 volts, add electrical loads by turning on electrical accessories until voltage reads below 12.5 volts. If the A/C clutch field coil current reading is zero, the coil is open and must be replaced. If the A/C clutch field coil current reading is above specifications, the coil is shorted and must be replaced.
COIL RESISTANCE TEST - 2.8L AND 4.0L ENGINES ONLY
- Disconnect and isolate the negative battery cable.
- Disconnect the wire harness connector from the A/C clutch field coil connector.
- Use an ohmmeter and measure the resistance of the clutch field coil at the field coil connector terminals.
- Refer to the following A/C Clutch Field Coil Specifications chart for the acceptable A/C clutch coil resistance. If the A/C clutch coil resistance reading is above specifications, the coil is shorted and must be replaced. If the A/C clutch coil resistance reading is below specifications, the coil is open and must be replaced.
| A/C Compressor | Current Draw | Coil Resistance |
|---|---|---|
| Zexel DKS-17DS (2.8L/4.0L engines) | 3.3 amps @ 12V ± 0.5V @ 25°C (77°F) | 4.02 ± 0.2 ohms @ 25°C (77°F) |
| Visteon HS-18 (3.7L engine) | 3.1-4 amps @ 12V ± 0.5V @ 21°C (70°F) | Not applicable |
A/C CLUTCH FIELD COIL SPECIFICATIONS
A/C CLUTCH PLATE 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.
Scheme 11
Examine the friction surfaces of the pulley and the clutch plate (2) for wear. The pulley and clutch 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 (1) for refrigerant oil. If refrigerant oil is found, the compressor shaft seal is leaking and the A/C compressor must be replaced.
Check the pulley bearing for roughness or excessive leakage of grease. Replace the pulley and bearing assembly, if required.
DIAGNOSIS AND TESTING
| WARNING | Disable the airbag system before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Disconnect and isolate the negative battery (ground) cable, then wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to take the proper precautions could result in accidental airbag deployment and possible personal injury or death. |
Note. For circuit descriptions and diagrams, refer to SYSTEM WIRING DIAGRAMS . The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.
- Disconnect and isolate the negative battery cable.
- Disconnect the wire harness connector from the blower motor resistor. See «REMOVAL»(ref-306135-S42728977322008120900000) .
- Using an ohmmeter, check for continuity between all of the blower motor resistor terminals. In each case there should be continuity. If OK, repair the wire harness circuits between the blower motor speed control and the blower motor resistor or blower motor as required. If not OK, replace the inoperative blower motor resistor.
The A/C pressure transducer is tested using a scan tool. Refer to HEATING & AIR CONDITIONING - ELECTRICAL DIAGNOSTICS for more information. Before testing the A/C pressure transducer, be certain that the transducer wire harness connection is clean of corrosion and properly connected. For the A/C to operate, an A/C pressure transducer voltage reading between 0.451 and 4.519 volts is required. Voltages outside this range indicate a low or high refrigerant system pressure condition to the powertrain control module (PCM). The PCM is programmed to respond to a low or high refrigerant system pressure by suppressing operation of the A/C compressor. Refer to A/C PRESSURE TRANSDUCER VOLTAGE for the possible conditions indicated by the transducer voltage reading.
| Voltage | Possible Indication |
|---|---|
| 0.0 | 1. No sensor supply voltage from PCM. |
| 2. Shorted sensor circuit. | |
| 3. Inoperative transducer. | |
| 0.150 TO 0.450 | 1. Ambient temperature below 10°C (50°F). |
| 2. Low refrigerant system pressure. | |
| 0.451 TO 4.519 | 1. Normal refrigerant system pressure. |
| 4.520 TO 4.850 | 1. High refrigerant system pressure. |
| 5.0 | 1. Open sensor circuit. |
| 2. Inoperative transducer. |
A/C PRESSURE TRANSDUCER VOLTAGE
When investigating an A/C system related noise, you must first know the conditions under which the noise occurs. These conditions include: weather, vehicle speed, transmission in gear or neutral, engine speed, engine temperature, and any other special conditions. Noises that develop during A/C operation can often be misleading. For example: What sounds like a failed front engine bearing or connecting rod, may be caused by loose bolts, nuts, mounting brackets or a loose compressor clutch assembly.
Drive belts are speed sensitive. At different engine speeds and depending upon drive belt tension, drive belts can develop noises that are mistaken for an A/C compressor noise. Improper drive belt tension can cause a misleading noise when the compressor clutch is engaged, which may not occur when the compressor clutch is disengaged. Check the accessory drive belt condition and tension as described in Cooling before beginning this procedure.
- Select a quiet area for testing. Duplicate the complaint conditions as much as possible. Turn the A/C compressor On and Off several times to clearly identify the compressor noise. Listen to the A/C compressor while the clutch is engaged and disengaged. Probe the A/C compressor with an engine stethoscope or a long screwdriver with the handle held to your ear to better localize the source of the noise.
- Loosen all of the compressor mounting hardware and retighten. Check the compressor clutch retainer. Be certain that the clutch field coil is mounted securely to the A/C compressor, and that the clutch plate and pulley are properly aligned and have the correct air gap.
- To duplicate high-ambient temperature conditions (high head pressure), restrict the air flow through the A/C condenser. Install a manifold gauge set or a scan tool to be certain that the discharge pressure does not exceed 2760 kPa (400 psi).
- Check the refrigerant system plumbing for incorrect routing, rubbing or interference, which can cause unusual noises. Also check the refrigerant lines and hoses for kinks or sharp bends that will restrict refrigerant flow, which can cause noises. See «DESCRIPTION»(ref-306135-S07299159802008120900000) .
- If the noise is from opening and closing of the high pressure relief valve, recover, evacuate and recharge the refrigerant system. See «STANDARD PROCEDURE»(ref-306135-S14322548632008120900000) .
- If the high pressure relief valve still does not seat properly, replace the A/C compressor. See «REMOVAL»(ref-306135-S11256117642008120900000) .
| WARNING | Refer to the applicable warnings and cautions for this system before performing the following operation. See WARNING , and CAUTION . Failure to follow the warnings and cautions could result in possible personal injury or death. |
Note. The A/C expansion valve should only be tested following testing of the A/C compressor.
Note. Liquid CO & amp;sup2; is required to test the A/C expansion valve. This material is available from most welding supply facilities. Liquid CO & amp;sup2; is also available from companies which service and sell fire extinguishers.
When testing the A/C expansion valve, the work area and the vehicle temperature must be 21° to 27°C (70° to 85°F). To test the expansion valve
- Connect a charging station or manifold gauge set to the refrigerant system service ports. Verify the refrigerant charge level.
- Close all doors, windows and vents to the passenger compartment.
- Set the A/C-heater controls so that the A/C compressor is operating, the temperature control is in the highest temperature position, the mode-air doors is directing air output to the floor and the blower motor operating is operating at the highest speed.
- Start the engine and allow it to idle. After the engine has reached normal operating temperature, allow the passenger compartment to heat up. This will create the need for maximum refrigerant flow into the A/C evaporator.
- If the refrigerant charge is sufficient, the discharge (high pressure) gauge should read 827 kPa to 1655 kPa (120 psi to 240 psi). The suction (low pressure) gauge should read 207 kPa to 345 kPa (30 psi to 50 psi). If OK, go to step 6 . If not OK, replace the inoperative A/C expansion valve. WARNING: Protect the skin and eyes from exposure to liquid CO & amp;sup2; or personal injury can result.
- If the suction (low pressure) gauge reads within the specified range, freeze the A/C expansion valve for 30 seconds using liquid CO & amp;sup2; or another suitable super-cold material. Do not spray R-134a or R-12 refrigerant on the A/C expansion valve for this test. The suction (low pressure) gauge reading should drop by 69 kPa (10 psi). If OK, go to step 7 . If not OK, replace the inoperative A/C expansion valve.
- Allow the expansion valve control head to thaw. The suction (low pressure) gauge reading should stabilize at 207 kPa to 345 kPa (30 psi to 50 psi). If not OK, replace the inoperative A/C expansion valve.
- When expansion valve testing is complete, test the overall A/C system performance. See «DIAGNOSIS AND TESTING»(ref-306135-S27707253392008120900000) .
| WARNING | Disable the airbag system before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Disconnect and isolate the negative battery (ground) cable, then wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to take the proper precautions could result in accidental airbag deployment and possible serious or fatal injury. |
Note. For circuit descriptions and diagrams, refer to SYSTEM WIRING DIAGRAMS . The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.
Prior to replacing the positive temperature coefficient (PTC) heater unit, check for any diagnostic trouble codes (DTCs) related to the engine control module (ECM), totally integrated power module (TIPM) and the heating-A/C system and repair as necessary. Refer to HEATING & AIR CONDITIONING - ELECTRICAL DIAGNOSTICS for more information.
- Disconnect and isolate the negative battery cable.
- Disconnect the wire harness connector from the PTC heater unit. See «REMOVAL»(ref-306135-S42843392162008120900000) .
- Using an ohmmeter, check for continuity between all of the PTC heater unit terminals. In each case there should be continuity. If OK, repair the wire harness circuits between the PTC heater unit and the TIPM. If NOT OK, replace the PTC heater unit.