VALVE, A/C Expansion
DESCRIPTION
 |
The A/C expansion valve controls the amount of refrigerant entering the A/C evaporator. The A/C expansion valve is of a thermostatic expansion valve (TXV) design and consists of an aluminum H-valve type body (1) with an inlet port (2), outlet port (3) and an integral thermal sensor (4).
The A/C expansion valve is located between the A/C refrigerant lines and the A/C evaporator in the engine compartment.
OPERATION
The A/C expansion valve controls the high-pressure, low temperature liquid refrigerant from the A/C liquid line and converts it into a low-pressure, low-temperature mixture of liquid and gas before it enters the A/C evaporator. A mechanical sensor in the A/C expansion valve monitors the temperature and pressure of the refrigerant leaving the A/C evaporator through the A/C suction line, and adjusts the orifice size at the liquid line port to let the proper amount of refrigerant into the evaporator to meet the vehicle A/C cooling requirements. Controlling the refrigerant flow through the A/C evaporator ensures that none of the refrigerant leaving the A/C evaporator is still in a liquid state, which could damage the A/C compressor.
| NOTE: |
Replacement of the refrigerant line O-ring seals is required anytime a refrigerant line is disconnected from the expansion valve. Failure to replace the rubber O-ring seals could result in a refrigerant system leak. |
The A/C expansion valve is factory calibrated and cannot be adjusted or repaired and must be replaced if inoperative or damaged.
DIAGNOSIS AND TESTING - A/C EXPANSION VALVE
Review the warnings and cautions
for this system before performing the procedure. Failure to follow
these instructions may result in serious injury or death.
WARNING:
| NOTE: |
The A/C expansion valve should only be tested following testing of the A/C compressor. |
| NOTE: |
Liquid CO² is required to test the A/C expansion valve. This material is available from most welding supply facilities. Liquid CO² 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 CO² 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 CO² 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 the expansion valve testing is complete, test the overall A/C system performance (Refer to 24 - Heating and Air Conditioning - Diagnosis and Testing) .
REMOVAL
Review the warnings and cautions
for this system before performing the procedure. Failure to follow
these instructions may result in serious injury or death.
WARNING:
| NOTE: |
3.6L engine model shown. 2.8L engine model similar. |
 |
- Disconnect and isolate the negative battery cable.
- Remove the engine trim cover.
- Recover the refrigerant from the refrigerant system (Refer to 24 - Heating and Air Conditioning/Plumbing - Standard Procedure) .
- Remove the nut (3) that secures the bracket (2) containing the A/C suction line (1) and A/C liquid line (5) to stud on the cowl panel (4).
-
Disengage the refrigerant
line bracket from the stud.
- On 3.6L engine models, remove the intake manifold (Refer to 09 - Engine/Manifolds/MANIFOLD, Intake - Removal) .
- Remove the nut (2) that secures the A/C liquid line (3) and A/C suction line (4) to the A/C expansion valve (1).
-
Disconnect the A/C
liquid and suction lines from the A/C expansion valve, remove and
discard the O-ring seals and position the refrigerant line assembly
out of the way.
- Remove the two bolts (3) that secure the A/C expansion valve (2) to the evaporator tube tapping block (1).
- Remove the A/C expansion valve from the evaporator tube tapping block and remove and discard the O-ring seals.
-
Install plugs in, or
tape over the opened refrigerant line and evaporator tube fittings
and all expansion valve ports.
INSTALLATION
Be certain to adjust the refrigerant
oil level when servicing the A/C refrigerant system .
Failure to properly adjust the refrigerant oil level will prevent
the A/C system from operating as designed and can cause serious A/C
compressor damage.
CAUTION:
| NOTE: |
When replacing multiple A/C system components, see the Refrigerant Oil Capacities chart to determine how much oil should be added to the refrigerant system (Refer to 24 - Heating and Air Conditioning/Plumbing/OIL, Refrigerant - Standard Procedure) . |
| NOTE: |
Replacement of the refrigerant line O-ring seals and gaskets is required anytime a refrigerant line is disconnected. Failure to replace the rubber O-ring seals and metal gaskets could result in a refrigerant system leak. |
| NOTE: |
3.6L engine model shown. 2.8L engine model similar. |
|
- Remove the tape or plugs from the opened refrigerant lines and evaporator tube fittings and all of the expansion valve ports.
- Lubricate new O-ring seals with clean refrigerant oil and install them onto the evaporator tube fittings. Use only the specified O-rings as they are made of a special material for the R-134a system. Use only refrigerant oil of the type recommended for the A/C compressor in the vehicle.
- Install the A/C expansion valve (2) onto the evaporator tube tapping block (1).
-
Install the two bolts (3) that secure the A/C expansion valve to the evaporator tube tapping block. Tighten the bolts to 11 N·m (97 in. lbs.).
- Lubricate new O-ring seals with clean refrigerant oil and install them onto the refrigerant line fittings. Use only the specified O-rings as they are made of a special material for the R-134a system. Use only refrigerant oil of the type recommended for the A/C compressor in the vehicle.
-
Connect the A/C liquid line (3) and A/C suction line (4) to the A/C expansion valve (1) and install the retaining nut (2). Tighten the nut to 8 N·m (70 in. lbs.).
- On 3.6L engine models, install the intake manifold (Refer to 09 - Engine/Manifolds/MANIFOLD, Intake - Installation) .
- Engage the refrigerant line bracket (2) onto the stud located on the cowl panel (4) and install the retaining nut (3). Tighten the nut securely.
- Install the engine trim cover.
- Reconnect the negative battery cable.
- Evacuate the refrigerant system (Refer to 24 - Heating and Air Conditioning/Plumbing - Standard Procedure) .
- Adjust the refrigerant oil level (Refer to 24 - Heating and Air Conditioning/Plumbing/OIL, Refrigerant - Standard Procedure) .
-
Charge the refrigerant system (Refer to 24 - Heating and Air Conditioning/Plumbing - Standard Procedure)
.