TXV Air Conditioning (A/C) System Diagnosis. Chevrolet Metro 1998

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1998 🢒 Metro 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 TXV Air Conditioning (A/C) System Diagnosis

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

Under conditions of high humidity, the air 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. This condition makes the humid air much harder to cool.

During hot, humid weather, dry dehumidified air coming from the A/C system evaporates more moisture on a person's skin. This 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.

Step

Action

Value(s)

Yes

Was the HVAC Compressor Controls System Check performed?

Go to Step 2

Go to HVAC Compressor Controls System Check

Turn the ignition switch to the LOCK position.
Inspect the following fuses:

•

The A/C

•

The HTR

•

The IG

Replace fuses as necessary.
Set the parking brake.
Start the engine.
Set the blower speed selector switch to any speed except the OFF position.
Press the air conditioning (A/C) switch to the ON position.
Turn the blower speed to the OFF position.
Turn the ignition switch to the LOCK position.
Inspect the fuses again.

Are any or all of the fuses open?

Go to Step 20

Go to Step 3

Turn the ignition switch to the ON position.
Turn the blower to the following speeds in the following order:

2.1.

OFF

2.2.

2.3.

MEDIUM 1

2.4.

MEDIUM 2

2.5.

HIGH

2.6.

OFF

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 moves toward the LOW position?

Go to Step 4

Go to Step 21

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 Step 22

Inspect for a loose, damaged or missing compressor drive belt. Refer to Drive Belt Replacement 1.0L or Drive Belt Replacement 1.3L in Engine Mechanical.

Is the action complete?

Go to Step 6

Inspect the engine coolant fan operation. Refer to DTC P0480 Cooling Fan Relay Control Circuit 1.0L or DTC P0480 Cooling Fan Relay Control Circuit 1.3L in Engine Controls.

Is the action complete?

Go to Step 7

Inspect the condenser for a restriction in the air flow.
Clean and/or repair the condenser as needed. Refer to Condenser Replacement .

Is the action complete?

Go to Step 8

Ensure that the ambient air temperature is at least 16°C (60°F) before continuing to the next step.
Start the engine.
Set the air mode to the VENT position.
Set the blower speed to the HIGH position.
Set the temperature control to the full COLD position.
Press the A/C switch to the ON position.

Does the compressor clutch engage?

Go to Step 9

Go to Step 11

Closely monitor the compressor for any unusual knocking or loud moaning noises and/or compressor drive belt slipping.
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.
Notice if the compressor drive belt is slipping.

Is the compressor noise excessive?

Go to Step 23

Go to Step 10

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

Does the line feel cold to the touch?

Go to Step 24

Go to Step 14

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

Are the LOW and the HIGH side pressures the same as or higher than the specified value?

345 kPa (50 psi)

Go to Step 25

Go to Step 12

Monitor and compare the LOW and the HIGH side pressure readings.

Are the LOW and the HIGH pressures within the specified values?

69-345 kPa (10-50 psi)

Go to Step 13

Add 0.45 kg (1 lb) of the refrigerant.
Inspect the system for refrigerant leaks. Refer to Leak Testing .

Did you find a refrigerant leak?

Go to Step 26

Go to Step 28

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.

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

Go to Step 15

Go to Step 18

Inspect the system for refrigerant leaks. Refer to Leak Testing .

Did you find a refrigerant leak?

Go to Step 26

Go to Step 16

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

Is the compressor clutch cycle rate more than the specified value?

8 cycles per minute

Go to Step 27

Go to Step 17

Start the engine.
Set the air mode control lever to the VENT position.
Set the blower speed selector switch to the HIGH position.
Set the temperature control lever all of the way to the COLD position.
Press the A/C switch to the ON position.
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.

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

Go to Step 27

Go to Step 28

Inspect the HIGH side pressure.

Does the compressor engage within the specified values?

196-3140 kPa (28-455 psi)

Go to Step 19

Go to Step 29

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

Does the compressor stay engaged outside the specified values?

196-3140 kPa (28-455 psi)

Go to Step 29

Go to Step 30

Refer to HVAC Compressor Clutch Does Not Engage .

Is the action complete?

Go to Step 3

Refer to HVAC Blower Controls System Check .

Is the action complete?

Go to Step 4

Refer to Temperature Control Cable Adjustment .

Is the action complete?

Go to Step 5

Refer to Noise Diagnosis in order to determine the cause of the excessive compressor noise.

Is the action complete?

Go to Step 10

Repair the restriction in the HIGH side of the refrigerant system.
Visually inspect for a line/pipe frost spot in order to locate the restriction.

Is the repair complete?

Go to Step 14

Refer to HVAC Compressor Clutch Does Not Engage .

Is the action complete?

Go to Step 9

Repair the refrigerant leak. Refer to Leak Testing .

Is the repair complete?

Go to Step 30

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

Is the action complete?

Go to Step 30

Discharge and recharge the system. Refer to Refrigerant Recovery and Recharging .

Is the action complete?

Go to Step 30

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

Is the repair complete?

Go to Step 30

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

Is the action complete?

Go to HVAC Compressor Controls System Check

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

Symptom	Cause	Correction
Hi 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.	Remove and inspect the expansion valve. Clean the expansion valve. 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/pipes for a restriction. Repair as necessary.
	The condenser fan is malfunctioning.	Refer to Condenser Fan Inoperative .
	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 as necessary. Refer to Air Conditioning Compressor Replacement .
	The engine is overheating.	Refer to Engine Overheating .
Hi Side Pressure Below Specifications	Insufficient refrigerant exists or leakage occurs.	Leak test the system and recharge. Refer to Leak Testing and Refrigerant Recovery and Recharging .
	The expansion valve opens too wide.	Refer to Thermal Expansion Valve Replacement .
	The compressor is malfunctioning.	Test the compressor and repair as necessary. Refer to Air Conditioning Compressor Replacement .
Low Side Pressure Above Specifications	The expansion valve opens too wide.	Refer to Thermal Expansion Valve Replacement .
	The heat sensing tube of the expansion valve is mounted improperly.	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 Air Conditioning Compressor Replacement .
Low Side Pressure Below Specifications	Insufficient refrigerant or leakage exists.	Leak test the system and recharge. Refer to Leak Testing and Refrigerant Recovery and Recharging .
	The expansion valve does not open wide enough.	Refer to Thermal Expansion Valve Replacement .
	A restriction exists in the hoses/pipes.	Inspect the hoses/pipes for a restriction. Repair as necessary.
Center Outlet Air Temperature Above Specifications	The refrigerant system is improperly 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 Air Conditioning Evaporator Core Replacement .
	Air leakage occurs in the air distribution system.	Refer to HVAC Blower Controls System Check .
	The temperature control door is malfunctioning.	Refer to Temperature Control Cable Adjustment .
	The compressor is malfunctioning.	Test the compressor and repair as necessary. Refer to Air Conditioning Compressor Replacement .
Center Outlet Air Temperature Below Specifications	Insufficient air volume exists (blower malfunction).	Refer to HVAC Blower Controls System Check .
Center Outlet Air Temperature Below Specifications	The evaporator temperature sensor is malfunctioning.	Refer to HVAC Compressor Controls System Check .