What is the appropriate pressure for an automotive refrigerant pressure gauge?
2 Answers
Depending on the ambient temperature, the normal working pressure of the refrigeration system is generally 3^6 bar for the low pressure and 10^25 bar for the high pressure. Below is relevant information about the refrigerant pressure gauge for air conditioning: 1. Why add Freon to the air conditioning system: Freon is the medium that transfers heat in the air conditioning refrigeration system. Without it, heat cannot be effectively exchanged, and the air conditioner cannot cool or heat. Therefore, once the air conditioner lacks Freon, external symptoms include poor cooling (heating) performance, failure to cool (heat), protective shutdown, water leakage from the indoor unit (sometimes spraying water), and ice formation on the indoor evaporator. There are also unseen issues—reduced lifespan of the air conditioner, wasted electricity, and damage to the air conditioner compressor. Thus, to use the air conditioner normally, there must be sufficient Freon. 2. How much Freon is appropriate to add: In high-temperature 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 0.3 MPa. In winter, adding Freon does not strictly follow the pressure gauge reading (the reference pressure is 1.8 MPa) but relies on the technician's experience or observing the needle's swing amplitude.
When tinkering with my car, I found the AC refrigerant pressure gauge to be quite important. The low-side reading should ideally be between 20 to 40 psi—too high and the compressor can burn out, too low and the cooling will be insufficient. For example, last week when I helped my neighbor recharge the system, with an ambient temperature of 30°C, the gauge needle stabilized between 25 to 35 psi, which was just right. If it's hot and the pressure rises to 40 psi, it's generally not a big issue, but it's more accurate to measure with the engine fan running. Different vehicle models have different requirements; SUVs or older cars might have a wider acceptable range. Overcharging can cause the return line to frost up, while undercharging leaves the cabin uncomfortably hot. I recommend beginners check the manual first, add refrigerant slowly in small amounts, and simultaneously check for leaks in the system—adding more won't help if there's a leak. DIY can be fun, but if you can't manage it, don't push your luck; take it to a professional shop. A damaged compressor is expensive to fix.
