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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Metro 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 TXV Air Conditioning (A/C) System Diagnosis

TXV Air Conditioning (A/C) System Diagnosis Insufficient Cooling

Step

Action

Yes

No

There are some conditions which are normal to the operation of the air conditioning (A/C) system that may lead an owner to wrongly suspect that a problem exists.

Under certain conditions of high humidity, the air that is discharged from the A/C system may not feel as cold as expected. This is because vaporized moisture in humid air heats more effectively than does dry air, making the humid air much harder to cool.

In terms of overall comfort, however, dryer, dehumidified air coming from the A/C system during hot, humid weather evaporates more moisture on a person's skin. This provides a cooling effect more than the air which is cooler but more humid.

This fact should be explained to an owner if a mechanical cause for a continuing complaint of insufficient cooling cannot be found.

1

Did you perform the HVAC System Check?

Go to Step 2

Go to HVAC System Check

2
  1. Turn the ignition switch to the LOCK position.
  2. Inspect the following fuses:
    3. • The A/C
    • The HTR
    • The IG
  3. Replace fuses as necessary.
  4. Set the parking brake.
  5. Start the engine.
  6. Set the blower speed selector switch to any speed except the OFF position.
  7. Press the air conditioning (A/C) switch to the ON position.
  8. Turn the blower speed selector switch to the OFF position.
  9. Turn the ignition switch to the LOCK position.
  10. Inspect the fuses again.

Are any of the fuses or all of the fuses open?

Go to HVAC Compressor Clutch Does Not Engage

Go to Step 3

3
  1. Turn the ignition switch to the ON position.
  2. Turn the blower to the following speeds in the following order:
    3. 2.1. OFF
    2.2. LOW
    2.3. MEDIUM 1
    2.4. MEDIUM 2
    2.5. HIGH
    2.6. OFF
  3. Turn the ignition switch to the LOCK position.

Does the blower motor speed increase at each speed level when the blower speed selector switch is moved towards the HIGH position and then decrease as the switch is moved towards the LOW position?

Go to Step 4

Go to HVAC System Check

4

Quickly move the temperature control lever from COLD to HOT and back to COLD in order to inspect the temperature door operation.

Do you hear the temperature door slamming at each end?

Go to Step 5

Go to Temperature Control Cable Adjustment

5

Inspect for the follow conditions: Refer to Drive Belt Replacement 1.0L or to Drive Belt Replacement 1.3L in Engine Mechanical.

    • A loose compressor drive belt
    • A damaged compressor drive belt
    • A missing compressor drive belt

Is the repair complete?

Go to Step 24

Go to Step 6

6

Inspect the engine cooling fan operation. Refer to the following procedures:

    •  DTC P0480 Cooling Fan Relay Control Circuit in Engine Controls 1.0 L
    •  DTC P0480 Cooling Fan Relay Control Circuit in Engine Controls 1.3 L

Is the repair complete?

Go to Step 24

Go to Step 7

7
  1. Inspect the condenser for a restriction in the airflow.
  2. Clean and/or repair the condenser if necessary. Refer to Condenser Replacement .

Is the repair complete?

Go to Step 24

Go to Step 8

8
  1. Inspect the compressor for seizing.
  2. Stop the engine.
  3. Disengage the compressor clutch.
  4. Rotate the compressor clutch plate, not the pulley, using your hand.

Does the compressor clutch plate turn freely?

Go to Step 9

Go to Compressor Replacement

9
  1. The ambient air temperature must be at least 16°C (60°F) before continuing to the next step.
  2. Start the engine.
  3. Set the air mode to the VENT position.
  4. Set the blower speed to the HIGH position.
  5. Set the temperature control to the coldest position.
  6. Press the A/C switch to the ON position.

Does the compressor clutch engage?

Go to Step 10

Go to Step 12

10
  1. Closely monitor the compressor for any unusual knocking or loud moaning noises and/or compressor drive belt slipping.
  2. Cycle the compressor clutch by pressing the A/C switch to the OFF position and back to the ON position. Verify the noise, if there is any noise.
  3. Notice if the compressor drive belt is slipping.

Is the compressor noise excessive?

Go to Noise Diagnosis - A/C System

Go to Step 11

11

Feel the liquid line between the condenser and the receiver/dryer. The line should feel warm.

Does the line feel cold?

Go to Step 21

Go to Step 14

12
  1. Turn the ignition switch to the LOCK position.
  2. Obtain a J 39183-C R-134a manifold gauge set. Verify that the manifold gauge set is calibrated correctly.
  3. Connect the HIGH side pressure gauge and the LOW side pressure gauge to the service ports on the vehicle.
  4. Inspect the HIGH side system pressure and the LOW side system pressure. Both pressures should be almost equal to each other.

Does the HIGH side pressure and the LOW side pressure measure 345 kPa (50 psi) or higher?

Go to HVAC Compressor Clutch Does Not Engage

Go to Step 13

13

Monitor the HIGH side pressure reading.

Is the HIGH side pressure 69-345 kPa (10-50 psi)?

Go to Step 15

Go to Step 22

14

Feel the evaporator inlet pipe, which is the small pipe, and the evaporator outlet pipe at the bulkhead. The evaporator inlet pipe should feel warm.

Does the evaporator inlet pipe feel colder than the evaporator outlet pipe?

Go to Step 15

Go to Step 18

15
  1. Perform the leak test on the refrigerant system. Refer to Leak Testing .
  2. Add 0.45 kg (1 lb) of the refrigerant as necessary.
  3. Evacuate and recharge the system. Refer to Refrigerant Recovery and Recharging .

Did you find a refrigerant leak?

Go to Step 20

Go to Step 16

16
  1. Add 0.45 kg (1 lb) of refrigerant.
  2. Monitor the compressor clutch cycle rate.

Is the compressor clutch cycle rate 8 cycles per minute or greater?

Go to Step 22

Go to Step 17

17
  1. Start the engine.
  2. Set the air mode control lever to the VENT position.
  3. Set the blower speed to the HIGH position.
  4. Set the temperature control lever to the coldest position.
  5. Press the A/C switch to the ON position.
  6. Feel the evaporator inlet pipe, which is the small pipe and the evaporator outlet pipe at the bulkhead. The evaporator inlet pipe should feel warm.

Does the evaporator inlet pipe feel colder than the evaporator outlet pipe?

Go to Step 22

Go to Step 20

18

Inspect the HIGH side pressure.

Does the compressor engage within 196-3140 kPa (28-455 psi)?

Go to Step 19

Go to Step 23

19
  1. Run the compressor.
  2. Monitor the clutch operation and the HIGH side pressure for 5 minutes.
  3. The compressor should disengage when the HIGH side pressure is outside the specified values.

Does the compressor remain engaged outside 196-3140 kPa (28-455 psi)?

Go to Step 23

Go to Step 24

20

Repair the refrigerant leak. Refer to Leak Testing and to Refrigerant Recovery and Recharging .

Is the repair complete?

Go to Step 24

--

21
  1. Repair the restriction in the HIGH side of the refrigerant system.
  2. Inspect the line and/or the pipe for a frost spot in order to locate the restriction.

Is the repair complete?

Go to Step 24

--

22
  1. Discharge the system.
  2. Inspect for a restricted expansion valve or for a HIGH side restriction. Refer to Thermal Expansion Valve Replacement .

Is the repair complete?

Go to Step 24

--

23

Replace the A/C refrigerant pressure switch. Refer to Pressure Cycling Switch Replacement .

Is the repair complete?

Go to Step 24

--

24

Perform the A/C system performance test. Refer to System Performance Test .

Is the repair complete?

Go to HVAC System Check

--

TXV Air Conditioning (A/C) System Diagnosis Reference Table

Symptom

Cause

High Side Pressure Above Specifications
    • The refrigerant is overcharged. Discharge and recharge the refrigeration system. Refer to Refrigerant Recovery and Recharging .
    • The expansion valve is frozen or clogged.
        1. Remove and inspect the expansion valve.
        2. Clean the expansion valve.
        3. If the expansion valve is already clean, replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
    • The is a restriction in the high side. Inspect the high side hoses and/or the pipes for a frost spot that indicates a restriction. Feel along the hoses and/or along the pipes for an abrupt temperature change. Repair as necessary.
    • The condenser fan is malfunctioning. Refer to the following procedures:
      •  Condenser Fan Inoperative
      •  DTC P0480 Cooling Fan Relay Control Circuit in Engine Controls 1.0 L
      •  DTC P0480 Cooling Fan Relay Control Circuit in Engine Controls 1.3 L
    • The condenser fins are dirty or bent. Clean or repair the condenser as necessary. Refer to Condenser Replacement .
    • The compressor is malfunctioning. Test the compressor, and repair the compressor as necessary. Refer to Compressor Replacement .
    • The engine is overheating. Refer to Engine Overheating .

High Side Pressure Below Specifications
    • There is insufficient refrigerant or leakage. Perform the leak test on the system, and recharge the system. Refer to Leak Testing and to Refrigerant Recovery and Recharging .
    • The expansion valve opens too wide. Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
    • The compressor is malfunctioning. Test the compressor, and repair the compressor as necessary. Refer to Compressor Replacement .

Low Side Pressure Above Specifications
    • The expansion valve opens too wide. Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
    • The heat sensing tube of the expansion valve is mounted incorrectly. Inspect the heat sensing tube location and repair as necessary. Refer to Thermal Expansion Valve Replacement .
    • The compressor is malfunctioning. Test the compressor and repair as necessary. Refer to Compressor Replacement .

Low Side Pressure Below Specifications
    • There is insufficient refrigerant or leakage. Leak test the system and recharge. Refer to Leak Testing and to Refrigerant Recovery and Recharging .
    • The expansion valve does not open wide enough. Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
    • There is a hose and/or a pipe restriction. Inspect the hoses and/or the pipes for a frost spot that indicates a restriction. Feel along the hoses and/or along the pipes for an abrupt temperature change. Repair as necessary.

Center Outlet Air Temperature Above Specifications
    • The refrigerant system is incorrectly charged. Discharge and recharge the refrigeration system. Refer to Refrigerant Recovery and Recharging .
    • The evaporator fins are dirty or bent. Clean or repair the evaporator as necessary. Refer to Evaporator Core Replacement .
    • There is air leakage in the air distribution system. Refer to HVAC System Check and to Air Delivery Improper .
    • The temperature control door is malfunctioning. Refer to Temperature Control Cable Adjustment .
    • The compressor is malfunctioning. Test the compressor, and repair the compressor as necessary. Refer to Compressor Replacement .

Center Outlet Air Temperature Below Specifications
    • There is insufficient air volume which indicates a blower malfunction. Refer to HVAC System Check .
    • The evaporator temperature sensor is malfunctioning. Refer to HVAC System Check and to Air Conditioning (A/C) Temperature Sensor Replacement .