What are the symptoms of a faulty expansion valve?
2 Answers
Automotive expansion valve failure symptoms include: 1. Low-pressure pipe not feeling cold to the touch; 2. Frost formation on the dryer and condenser; 3. No hissing sound heard at the expansion valve or condenser. More information about the expansion valve is as follows: 1. The principle of the expansion valve controller is: The system flow is controlled via an electromagnetic coil as the medium. Before the electromagnetic coil is energized, the valve needle is in an open state. After the electromagnetic coil is energized, the opening degree of the valve needle is controlled by the voltage on the electromagnetic coil to regulate the flow of the expansion valve. 2. The method for checking the condition of the expansion valve is: Connect the expansion valve to the high and low-pressure ends of the manifold pressure gauge, with the middle hose connected to the charging valve and injecting refrigerant; Place the capillary tube of the expansion valve into a water tank, observing the water temperature in the tank and the pressure on the high-pressure gauge; Operate the high-pressure manual valve to make the high-pressure gauge pointer reach 490kpa, allowing the refrigerant to discharge from the expansion valve in a gaseous state; If the intersection point of the water temperature and high-pressure gauge pressure values falls between the water temperature and high-pressure curves, it indicates the expansion valve is functioning normally. If not between the two curves, the expansion valve should be repaired or replaced.
Speaking of the expansion valve failure, I've driven quite a few cars and actually encountered this issue several times. The expansion valve controls the refrigerant flow in the AC system. Once it gets clogged or stuck, the refrigerant can't circulate properly, and the AC stops cooling—blowing out hot air like a heater. My old sedan had this problem last time; the evaporator was completely frozen over, and the compressor was roaring like it was about to explode. Driving with fogged-up windows was extremely dangerous. The repair shop found the expansion valve completely corroded, and replacing the part plus cleaning the system fixed it. A faulty expansion valve can also cause refrigerant leaks and skyrocketing pipeline pressure, damaging the entire AC system. So, if your AC acts up, don’t delay—get it professionally checked ASAP. Don’t end up like me, sweating bullets on the highway with regrets.
