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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 HVAC 🢒 Heating, Ventilation, and Air Conditioning 🢒 TXV Air Conditioning (A/C) System Diagnosis

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

Symptom

Correction

Low Side Pressure

High Side Pressure

150-300 kPa

(21-43 psi)

1275-1670 kPa

(185-244 psi)

Normal

Vacuum

500-600 kPa

(71-85 psi)
    • Expansion valve is frozen or clogged.
    • Heat sensing tube leaking, preventing refrigerant flow.
    • Frost may be on tubing between the receiver/dryer and the expansion valve.

Replace the expansion valve and the receiver dryer, and evacuate and recharge the system. Refer to the following:

Normal to vacuum

Normal to 690-980 kPa

(100-142 psi)

The expansion valve is frozen due to moisture in the system, temporarily shutting down the refrigeration cycle. Replace the expansion valve and the receiver dryer, and evacuate and recharge the system. Refer to the following:

50-100 kPa

(4-14 psi)

690-980 kPa

(100-142 psi)

Insufficient refrigerant in system. Leak test the system, repair and recharge. Refer to Leak Testing and Refrigerant Recovery and Recharging .

400-600 kPa

(57-85 psi)

690-980 kPa

(100-142 psi)

Internal leak in compressor. Replace the compressor. Refer to Air Conditioning Compressor Replacement .

250-300 kPa

(36-43 psi)

1960-2450 kPa

(285-355 psi)
    • System overcharged. Refer to Refrigerant Recovery and Recharging .
    • Condenser fan malfunction. Refer to Cooling Fan Inoperative .
    • Condenser airflow restricted. Clean or repair the condenser as necessary. Refer to Condenser Replacement .
    • Engine overheating. Refer to Engine Overheating .
    • Air in A/C system due to improper evacuating. Replace the receiver dryer and evacuate and recharge the system. Refer to Receiver Dehydrator Replacement and Refrigerant Recovery and Recharging .

300-400 kPa

(43-57 psi)

1960-2450 kPa

(285-355 psi)
    • Expansion valve malfunction. Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
    • Refrigerant flow not regulated properly.
    • Frost may be on low side tubing.

Normal to low

Low

Low side restriction. Inspect for a kinked tube/hose, or a clogged suction screen.

Normal to low

Normal to high

High side restriction. Visually inspect for frost spot. Feel along tubing for temperature change.

Center Outlet Air Temperature Above Specifications
    • Improper refrigerant charge. Evacuate and recharge the system. Refer to Refrigerant Recovery and Recharging .
    • Evaporator airflow restricted. Clean or repair the evaporator as necessary. Refer to Air Conditioning Evaporator Core Replacement .
    • Air leakage within the heater case. Refer to Air Delivery Improper .
    • Temperature control door malfunction. Refer to Temperature Control Cable Adjustment .
    • Compressor malfunction. Replace the compressor. Refer to Air Conditioning Compressor Replacement .

Center Outlet Air Temperature Below Specifications
    • Insufficient air volume. Refer to Symptoms - HVAC Systems - Manual .
    • Evaporator temperature sensor malfunction. Refer to Symptoms - HVAC Systems - Manual .

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

Step

Action

Yes

No

Important: Some conditions which are normal to correct A/C system is operation may lead an owner to wrongly suspect a problem exists.

Under conditions of high humidity, the air discharged from the A/C system may not feel as cold as expected. This is because the 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, the dryer, dehumidified air coming from the A/C system during hot, humid weather, evaporates more moisture on a person's skin and provides more of a cooling effect than air which is cooler but more humid.

This fact should be explained to an owner if a mechanical cause for a persistent complaint of insufficient cooling cannot be found. Refer to Symptoms - HVAC Systems - Manual .

1
  1. Inspect the compressor clutch wire connector for an open or poor connection. Refer to HVAC Compressor Clutch Does Not Engage and/or Testing for Intermittent Conditions and Poor Connections .
  2. Inspect the following fuses:
    3. • The A/C
    • The HTR
    • The IG
    • The DEF
    • The Blower

Did you find and correct the condition?

Go to Step 18

Go to Step 2

2
  1. Inspect the temperature control and cable operation.
  2. Move the temperature control lever from the coldest to the hottest positions.
  3. Listen for the door hitting at each end.
  4. Repair as necessary. Refer to Temperature Control Cable Adjustment .

Did you find and correct the condition?

Go to Step 18

Go to Step 3

3

Inspect the blower motor for proper operation. The blower motor speed should increase at each speed level as the switch is turned towards HIGH and then decrease as the switch is turned towards LOW.

Did you find and correct the condition?

Go to Step 18

Go to Step 4

4

Inspect for a loose, damaged, slipping, or missing compressor drive belt. Refer to Drive Belt Replacement .

Did you find and correct the condition?

Go to Step 18

Go to Step 5

5

Inspect the condenser fan for correct operation. Refer to Cooling Fan Inoperative .

Did you find and correct the condition?

Go to Step 18

Go to Step 6

6
  1. Inspect the condenser for a restriction in airflow.
  2. Clean and/or repair the condenser as necessary. Refer to Condenser Replacement .

Did you find and correct the condition?

Go to Step 18

Go to Step 7

7
  1. Inspect the compressor for seizure.
  2. Stop the engine.
  3. Disengage the compressor clutch.
  4. Rotate the compressor clutch plate, not the pulley, by hand.

Does the compressor clutch plate turn freely by hand?

Go to Step 8

Go to Air Conditioning Compressor Replacement

8
  1. The ambient air temperature must be at least 16°C (60°F).
  2. Connect the pressure gages of a properly calibrated J 39183-C R-134a manifold gage set to the High and Low side service ports on the vehicle.
  3. Both the High and Low side pressures should be almost equal to each other.

Are the High and the Low side pressures 345 kPa (50 psi) or higher?

Go to Step 9

Go to Step 13

9
  1. Start the engine and run at idle.
  2. Set the blower speed to the highest position.
  3. Set the temperature control to the coldest position.
  4. Set the mode control to the I/P outlet position.
  5. Press the A/C switch to the ON position.

Does the compressor clutch engage?

Go to Step 10

Go to HVAC Compressor Clutch Does Not Engage

10
  1. 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.
  3. Notice if the compressor drive belt is slipping.

Is there excessive compressor noise?

Go to Air Conditioning Compressor Replacement

Go to Step 11

11
  1. Visually inspect the lines for a frost spot indicating a restriction.
  2. Feel the lines for an abrupt temperature change. The high side components should feel warm/hot from the compressor outlet to the expansion valve.
  3. The low side components should feel cool/cold from the evaporator outlet to the compressor inlet.
  4. Repair as necessary.

Did you find and correct the condition?

Go to Step 18

Go to Step 12

12

Feel the evaporator inlet pipe (the small pipe) and the evaporator outlet pipe at the bulkhead. The evaporator inlet pipe should feel warm to the touch. The evaporator outlet pipe should feel cool to the touch.

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

Go to Step 13

Go to Step 15

13
  1. Leak test the refrigeration 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 .

Is a leak present?

Go to Step 14

Go to Step 16

14

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

Is the repair complete?

Go to Step 18

--

15
  1. Run the compressor.
  2. Monitor the clutch operation and the system pressures for 5 minutes.
  3. The compressor should disengage when the system pressure is outside the specified values.

    4. High Side Pressure Range
    1275-1670 kPa (185-244 psi)

    Low Side Pressure Range
    150-300 kPa (21-43 psi)

Does the compressor stay engaged outside the specified values?

Go to Step 17

Go to Step 16

16
  1. Discharge the system.
  2. Inspect for a restricted or malfunctioning expansion valve. Refer to Thermal Expansion Valve Replacement .

Is the repair complete?

Go to Step 18

--

17

Replace the A/C refrigerant pressure switch. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .

Is the repair complete?

Go to Step 18

--

18

Operate the system in order to verify the repair. Refer to Air Conditioning (A/C) System Performance Test .

Did you correct the condition?

System OK

Go to Step 1