How to Read an Automotive Air Conditioning Gauge?
3 Answers
There are two gauges on an automotive air conditioning system: the red one indicates high pressure, while the blue one shows low pressure. The units displayed on these gauges may vary, including bar, kilopascal (kpa), pounds per square inch (psi), etc. The conversion formula is: 1bar=100kpa=14.5psi. Below is a detailed explanation of how to interpret an automotive air conditioning gauge: Insufficient Refrigerant: When the automotive air conditioning pressure gauge displays low readings on both low and high pressure sides, it indicates insufficient refrigerant. This is a common issue in older vehicles where refrigerant leakage may occur. After inspection, simply recharging the refrigerant can resolve the problem. Expansion Valve Malfunction: When the automotive air conditioning pressure gauge shows high readings on both low and high pressure sides, it suggests a stuck-open expansion valve. Poor cooling performance accompanied by elevated low and high pressure readings typically means the expansion valve is stuck open, allowing air into the refrigeration system and causing pressure mixing, which degrades cooling efficiency. Replacing the expansion valve will solve this issue.
When I check the car air conditioning gauge myself, it feels like reading a simple report. The gauge typically includes several key items: first is the refrigerant pressure, usually marked with high and low pressure values on the gauge. The normal range is 1.5-2.5 MPa for high pressure and 0.15-0.25 MPa for low pressure. If the readings are too high or too low, it may indicate leakage or blockage. Next is the comparison of air vent temperatures—the gauge will have you measure the temperature difference between inside and outside the car, with an ideal difference of 10-15°C. A smaller difference suggests poor cooling. You also need to check the fan operation status—it should run without unusual noises. Every time I wash my car, I take a quick look, using a screwdriver to open the gauge’s needle hole and read the data. If I notice any abnormalities, I contact a professional shop for a follow-up check. This helps avoid sudden air conditioning failures in the summer. Remember to keep the windows ventilated while observing data changes—preventive checks can extend the AC’s lifespan by several years.
As an experienced professional, I always approach interpreting automotive air conditioning inspection sheets from a technical perspective, dividing the table into several key sections: The first part involves refrigerant system checks, focusing on pressure parameters—ensuring high and low pressure values fall within the 1.8-2.2 MPa and 0.18-0.25 MPa ranges respectively. Exceeding these limits may indicate compressor failure or a dirty radiator. The second section records temperature, where the deviation between outlet air temperature and set value should be less than 5°C; larger discrepancies suggest expansion valve malfunction. The third part examines fan operation for smooth running, low noise, and normal airflow. Finally, check for leakage indicators marked with √/× symbols on the sheet. During routine services, I carry a multimeter to assist with readings and pinpoint root causes directly when issues arise. I recommend owners spend 10 minutes reviewing the sheet before each seasonal change. If data appears erratic, taking smartphone photos facilitates discussions with repair shops—saving time, reducing hassle, and preventing major overhauls.
