What is the pressure when the car air conditioning is not activated?
4 Answers
Car air conditioning normal high pressure should be 3-7MPa (13-17kg/cm2 or 190-250Lbf/in2); normal low pressure should be between 0.15-0.25MPa (5-5kg/cm2 or 20-35Lbf/in2). Below is relevant information about car air conditioning: Introduction to Car Air Conditioning: The car air conditioning system is a device that cools, heats, ventilates, and purifies the air inside the vehicle compartment. It provides a comfortable environment for passengers, reduces driver fatigue, and improves driving safety. The air conditioning system has become one of the indicators to measure whether a car is fully equipped. Disadvantages: When the air conditioning is on, passengers are advised not to smoke in the car. Since the air inside circulates in a relatively enclosed environment when the air conditioning is on, smoke is difficult to dissipate, and tiny particles in the smoke can adhere to the air conditioning intake filter, causing long-lasting odors in the car. Regularly perform professional air conditioning system cleaning and deodorizing maintenance.
When working at the repair shop, I often encounter car owners asking about pressure issues when the air conditioning fails to start. If the compressor isn't running, the system is in a static equilibrium state, with pressure fluctuating between 50 to 70 psi, mainly depending on ambient temperature—for example, around 60 psi at 25°C room temperature, and possibly close to 70 psi at 30°C. If the pressure is too low, say down to 30 psi, it might be due to refrigerant leakage causing poor AC performance; if it's too high, exceeding 80 psi, it could indicate a blocked pipeline or excessive impurities. It's recommended to use a dedicated pressure gauge to measure the low-pressure port—simple and quick. You can buy a small tool for home use to check this, costing just a few dozen bucks. If you spot an issue, don't push through—get it fixed at a repair shop promptly to avoid AC failure while driving, which could affect safety. The AC will start smoothly only when the pressure is normal. Regular maintenance should focus on seal rings and pipeline cleanliness to minimize problems.
As a regular car owner, I was curious about the pressure when the AC is off right after buying my car. It turns out that when the compressor is idle, the high and low pressure ports have equal pressure, typically ranging between 50-70 psi at normal temperatures, and slightly higher when it's warmer. I used a DIY pressure gauge to measure it, which was simple and straightforward. If the pressure is too low, it might indicate a refrigerant shortage needing a refill; if it's too high, the cooling system could be clogged—don't tamper with it yourself to avoid causing issues. After measuring, I recorded the values and dates for easy tracking, ensuring early detection of any problems for professional inspection. Pressure is a health signal for your AC—only when it's normal can the system start reliably, making your drive more reassuring.
After driving for many years, when the AC doesn't start, I focus on checking the pressure values. Generally, at ambient temperatures of 20-30°C, the pressure should be in a balanced state of 50-70 psi. Too high, like above 85 psi, risks explosion, while too low, like below 40 psi, can lead to gas leakage. Using a multimeter and pressure gauge together is the safest way to measure. Once, I ignored abnormal pressure and ended up with a broken AC on the road—it was unbearably hot. With stable pressure, the startup is smooth, ensuring driving safety.
