What is the normal low pressure for car air conditioning?
2 Answers
Car air conditioning pressure is divided into high pressure and low pressure. Under normal operating conditions, the low pressure typically ranges between 1.0-2.5 bar, while the high pressure ranges between 15-18 bar. Below are the detailed explanations: Relationship between air conditioning pressure and compressor: When the engine throttle is increased, the measured low pressure should decrease with the engine speed—the faster the speed, the greater (or quicker) the pressure drop. This indicates good compressor performance; otherwise, it suggests a compressor malfunction. Normal pressure variations in car air conditioning: At idle, if the ambient temperature is high (e.g., under direct summer sunlight), the high pressure may be slightly higher, reaching up to approximately 2.5-2.8 MPa, but it generally does not exceed 3.1 MPa. If the low pressure is higher or lower than this range, it indicates improper expansion valve regulation. Compressor issues are not included in this category. Factors affecting air conditioning system pressure: The pressure in a car air conditioning system is influenced by various external conditions, such as ambient temperature, engine speed, condenser cooling conditions, etc. Therefore, the standard for testing car air conditioning system pressure is based on specific ambient temperatures, compressor speeds within a certain range, and condenser cooling under certain conditions, rather than a fixed standard.
As a seasoned DIY car enthusiast, I find the low-pressure side of AC systems quite nuanced. During summer, normal operating pressure ranges between 20-35 PSI (1.5-2.5 bar). The most accurate reading comes after running the AC for about 10 minutes. Pressure below 20 indicates potential refrigerant leakage - older vehicles often develop leaks at pipe joints due to aging. Pressure exceeding 35 might suggest clogged condenser fins (like with leaves). Once my car showed only 15 PSI, which turned out to be a blocked receiver-drier that required replacement. Note that readings fluctuate with ambient temperature - stationary vehicles on hot days show higher pressures that stabilize when moving.
