What is the method to determine if an expansion valve is functioning properly?
2 Answers
To determine if an expansion valve is functioning properly: 1. Connect the expansion valve to the high and low-pressure ends of the manifold gauge, with the middle hose connected to the injection valve to introduce refrigerant. 2. Place the capillary tube of the expansion valve into a water tank and observe the water temperature and the pressure on the high-pressure gauge. 3. Operate the high-pressure manual valve to bring the high-pressure gauge needle to 490 kPa, allowing refrigerant to discharge from the expansion valve in gaseous form. 4. If the intersection of the water temperature and high-pressure gauge pressure values falls between the water temperature and high-pressure curves, the expansion valve is functioning normally. If it does not fall between these curves, the expansion valve should be repaired or replaced. Common symptoms of expansion valve failure include: 1. The low-pressure pipe not feeling cold to the touch. 2. Frost forming on the dryer or condenser. 3. No hissing sound heard at the expansion valve or condenser.
I often work on my car's air conditioning system myself, and the expansion valve is a key component that controls refrigerant flow. To check if it's working properly, first start the engine and turn the AC to maximum cooling, then observe the temperature of the air coming from the vents. If the air is warm or not cold at all, but the compressor is still running, this suggests the valve may be clogged or stuck. Next, you can feel the high and low-pressure lines of the AC system with your hand; normally, the high-pressure line should be hot to the touch, while the low-pressure line should be cold. If the low-pressure line is also hot or has excessive frost buildup, the valve might be malfunctioning. Also, check around the expansion valve for any oil stains or signs of refrigerant leakage, which indicate poor sealing. For more accuracy, I use a manifold gauge to measure the pressure: the high pressure should be stable between 200-250 psi, and the low pressure between 30-40 psi. If the readings fluctuate wildly or are abnormally high, the valve is definitely faulty. If you can't handle these checks yourself, I recommend going directly to a repair shop and letting a technician diagnose it with professional tools.
