Solved: How to Test Vehicles AC Expansion Valve?

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The AC Expansion Valve is the component of a refrigeration system that regulates the rate of flow of refrigerant into the evaporator as governed by the action of the remote bulb-sensing tailpipe temperatures.

Before testing the Expansion valve.Its advisable to Inspect the valve.

How to Inspect Vehicles A/C Expansion Valve?

http://repairhelpcenter.blogspot.com/2011/11/how-to-inspect-vehicles-ac-expansion.html

Inspecting the expansion valve will help you to understand the problem.
For testing AC expansion valve,follow the procedure as follows :----

It must be noted that it is not always possible to performance test the thermostatic expansion valve (TXV or TEV) in the car. Suction pressure regulators and/or pressure switches often prevent valid testing. If this is the case, then the TXV may be removed from the car for bench testing.

It used to be the custom to test an expansion valve by releasing R-12 refrigerant onto the sensing bulb to freeze it. This is no longer allowed or cost effective. A CO2 fire extinguisher will work to test an expansion valve.

NOTE

Testing the expansion valve requires special tools and equipment that few technicians have. Hit and miss repairs and adjustments may be more expensive than replacement, even for the experienced technician.

Testing the TXV or TEV inside the car:

Remove the protective caps from the service valve stems. Some caps are made of metal and can be removed by hand.
Remove the protective caps from the service ports.

CAUTION
Remove the caps slowly to ensure that no refrigerant leaks past the service valve.

Connect the manifold gauge service hoses to the compressor.
Connect the low-side manifold hose to the suction side of the compressor.
Connect the high-side manifold hose to the discharge side of the compressor.
Make sure the hand shutoff valves are closed on the manifold set before the next step.
Use a service valve wrench and rotate the suction-side valve stem two or three turns clockwise.
Repeat the procedure in step 1 with the discharge service valve stem.
Start the engine and adjust the engine speed to 1,000-1,200 r/min.
Adjust all air-conditioning controls to maximum (MAX) cooling.
Operate the system for 10-15 minutes.

For abnormally low-side gauge readings:

Observe the low-side gauge reading. If abnormally low, then place a warm rag (125° F or 52°C) around the TXV body.
Observe the low-side gauge. If the pressure rises to normal, or near normal, then moisture in the system is indicated. (To correct moisture in the system, replace the desiccant receiver/drier or accumulator). Evacuate, charge, and re-test the system. If pressure does not rise, proceed to next step.
Remove the TXV remote bulb from the evaporator outlet and warm it in the hand or in a warm (125° F or 52°C) rag.
Observe the low-side gauge pressure. If the pressure rises, then the remote bulb was probably improperly placed. (To correct the rise in pressure, reposition the remote bulb, insulate, and re-test the system.) If the pressure does not rise, proceed with step 5.
If the low-side reading is abnormally low and steps 1 through 4 do not correct the problem; then remove the TXV from the system and do the bench testing procedure outside the vehicle.

For abnormally high-side gauge readings:

If the low-side gauge reading is abnormally high, then remove the remote bulb from the evaporator outlet and place it in an ice-water (H20) bath. Rock salt added to the ice water (H20) will lower the temperature to 32° F (0°C).
If the pressure falls to normal, or near normal, the problem may be: a lack of insulation at the remote bulb. Re-insulate the area and re-test.
If the pressure does not fall to normal or near normal, remove the TXV, and bench test TXV outside the car.
Conclude the test: turn off air conditioning controls. Reduce the engine speed to idle and stop the engine. Remove the manifold and gauge set.

Testing the TXV or TEV outside the car:

Close the high- and low-side manifold hand valves.
Remove the low-side service hose at the manifold.
Install a 1/4-inch female flare coupler to the low-side manifold.
Install a 1/4-inch male flare tee to the flare coupler at the low-side.
Reinstall the low-side manifold hose to the 1/4-inch flare tee.
Install a 1/4-inch test cap, drilled to 0.026 inch (0.66 mm), to the 1/4 inch.
Install the TXV inlet x 1/4-inch male-flare adapter to the inlet of the TXV.
Install the TXV inlet x 1/4-inch male-flare adapter to the outlet of the TXV.
Connect the low-side manifold hose to the expansion valve outlet.
Connect the high-side manifold hose to the expansion valve inlet.
Prepare nitrogen cylinder and regulator for service.
Adjust the nitrogen regulator to exactly 70 psig.
Fill an insulated container with cracked ice and add water (H2O). Use a thermometer to indicate when the temperature is 32° F (0°C), if necessary add salt and stir the mixture.
Heat water in a separate container until it reaches 125°F ( 52°C).

Testing the Expansion Valve for Maximum Flow:

Place the thermostatic expansion valve remote bulb into a container of water (H2O) heated to 125° F (52°C).
Open the high-side gauge manifold hand valve and adjust to exactly 70 psig (483kPa).
Read the low-side gauge. The maximum flow test should be 43-55 psig (296-379 kPa). Readings over 55 psig 379 kPa indicate a flooding valve. A reading under 43 psig (296 kPa) indicates a starving valve.

Testing the Expansion Valve for Minimum Flow:

Place the thermal bulb into a container of liquid at 32° F (0°C).
Open the high-side gauge manifold hand valve and adjust to exactly 70 psig (483kPa).
Read the low-side gauge.
Refer to the conversion charts for the proper low-side reading. The low-side gauge must be within the limits specified in the conversion chart if the valve is to pass the minimum flow test.

NOTE

The valve superheat settings corresponding to the valve outlet pressure readings are for CFC-12 expansion valves only.

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This details will help.Thanks.

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Also if you have better understanding of other car AC cooling system parts,then it will help more to troubleshoot the problem.

Check the list below or more help.

Its always advisable to know the AC components working and testing procedure,before replacing any part.

For more details regarding cars AC components.Check out the list of links below:---