How to Read the Gauge on an Air Conditioning Refrigerant Pressure Meter?
3 Answers
Depending on the ambient temperature, the low pressure during normal operation of the refrigeration system generally ranges between 3 to 6 bar, while the high pressure ranges between 10 to 25 bar. Below is an introduction to the air conditioning refrigerant pressure meter: Why Add Freon to Air Conditioners: Freon serves as the medium for heat transfer in the air conditioning refrigeration system. Without it, heat cannot be effectively exchanged, and the air conditioner cannot cool or heat. Therefore, if the air conditioner lacks Freon, symptoms may include poor cooling (or heating), failure to cool (or heat), protective shutdown, water leakage from the indoor unit (sometimes spraying water), and ice formation on the indoor evaporator. There are also less visible issues—reduced lifespan of the air conditioner, wasted electricity, and damage to the air conditioner's compressor. Hence, sufficient Freon is essential for normal air conditioner operation. How Much Freon Should Be Added to an Air Conditioner: During hot summer weather (when the ambient temperature is above 32°C), the pressure gauge needle should stabilize at 0.45 MPa. In spring and autumn, it should be around 0.3 MPa. In winter, adding Freon does not strictly follow the pressure gauge reading (the reference pressure is 1.8 MPa). Instead, it relies on the technician's experience or observing the swing amplitude of the pressure gauge needle.
I've been repairing cars for over twenty years, and reading the pressure gauge for AC refrigerant charging is very common. First, connect the high and low-pressure hoses to the AC system—the ports are usually color-coded. The gauge has a needle pointing to the pressure reading, measured in PSI or Bar, with the outer scale clearly marked. When taking a reading, ensure the AC is running and wait for the needle to stabilize. Don’t forget ambient temperature affects it—readings are lower in cold weather and higher in hot weather; the manual has a compensation chart. Safety first: excessive pressure can burst hoses, while too little won’t cool effectively. I always remind beginners to determine the refrigerant amount based on accurate readings—don’t cut corners. Check that valves are tightly closed; leaks are a common mistake. Regular maintenance, like keeping the gauge clean, ensures accuracy—a stuck needle gives false readings.
I've only been learning car repair for half a year, and my master taught me how to read the pressure gauge. Simply put, after connecting the pipe, the number the dial pointer points to is the pressure, with the unit PSI often marked in small print. The high and low pressure gauges are different, with the high pressure gauge having a red pointer and the low pressure gauge a blue one. Wait for the air conditioning to run for a few minutes until the pointer stabilizes before reading the number, don't rush. If it's too low, you need to add refrigerant; if it's too high, you need to release some. The first time I misread it, I didn't account for the temperature and added too much refrigerant, which affected cooling. Now I know that when it's hot outside, the reading tends to be higher, so I need to lower the target value a bit. Remember to close the valves for safety; leaking refrigerant is troublesome and harmful to the environment. Watch more videos to practice, and you'll get the hang of it with practice.
