Service Precaution: Horizontal expansion valves in r1234yf systems
In automotive A/C systems, the expansion valve regulates the flow of high-pressure, high-temperature liquid refrigerant to the evaporator, creating a pressure drop that leads to a significant temperature reduction. This process enables efficient absorption of heat from ambient air, which produces cool air for the vehicle's interior.
Generally, the expansion valve is located at the engine firewall on the passenger side of the vehicle in a vertical position, but some late model vehicles with R1234yf systems may have the expansion valve in a horizontal position.
R1234yf systems with the expansion valve in a horizontal position may complicate A/C system diagnosis because the horizontal position limits lubrication of the expansion valve's internal plunger. If the internal plunger gets stuck in an open or closed position, A/C performance will suffer.
When diagnosing an R1234yf system where the expansion valve is in a horizontal position, take note of the following precautions and recommendations for service and diagnosis: