A/C EXPANSION VALVE

WARNING: Refer to the applicable warnings and cautions for this system before performing the following operation. Failure to follow the warnings and cautions may result in possible serious or fatal injury.

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 21º to 27º C (70º to 85º F). To test the expansion valve:

1. Connect a charging station or manifold gauge set to the refrigerant system service ports. Verify the refrigerant charge level.

2. Close all doors, windows and vents to the passenger compartment.

3. 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.

4. 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.

5. 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 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.

6. 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 7. If not OK, replace the inoperative A/C expansion valve.

7. 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.

8. When expansion valve testing is complete, test the overall A/C system performance.