Expansion Valve: Testing and Inspection

NOTE: Expansion valve tests should be performed after compressor tests.

Review Safety Precautions and Warnings. The work area and vehicle temperature must be 21°C to 27°C (70°F to 85°F). To test the expansion valve:

NOTE: Liquid C02 is required to test the expansion valve. It is available from most welding supply facilities. C02 is also available from companies which service and sell fire extinguishers.

1. Connect a charging station or manifold gauge set to the refrigerant system service ports. Verify the refrigerant charge level using the sight glass method.
2. Disconnect cable at the water control valve. Slide the water valve open.
3. Disconnect wire connector at Dual Pressure Cut Off switch. Using a jumper wire, jump terminals inside wire connector boot.
4. Set heater A/C control to A/C, full heat, FLOOR, and high blower.
5. Start the engine and allow to idle (1000 rpm). After the engine has reached running temperature, allow the passenger compartment to heat up. This will create the need for maximum refrigerant flow into the evaporator.
6. If the refrigerant charge is sufficient, discharge (high pressure) gauge should read 965 to 1655 kPa (140 to 240 psi). Suction (low pressure) gauge should read 140 kPa to 207 kPa (20 psi to 30 psi). If system cannot achieve proper pressure readings, replace the expansion valve. If pressure is correct, proceed with test.

WARNING: PROTECT SKIN AND EYES FROM CONTACTING C02 PERSONAL INJURY CAN RESULT.

7. If suction side low pressure is within specified range, freeze the expansion valve control head for 30 seconds. It will be necessary to remove the blower motor to access the expansion valve. Refer to Blower Motor Removal. Use a super cold substance (liquid C02). Do not spray R-134 or R-12 Refrigerant on the expansion valve for this test. Suction side low pressure should drop to -50 kPa (-15 in. Hg) If not, replace expansion valve.
8. Allow expansion valve to thaw. The low pressure gauge reading should stabilize at 140 kPa to 240 kPa (20 psi to 30 psi). If not, replace expansion valve.
9. When expansion valve test is complete, test A/C overall performance. Remove all test equipment before returning vehicle to use.