What is the normal pressure for automotive air conditioning R134a?
3 Answers
When testing automotive air conditioning pressure, the normal range is generally that the high pressure should not exceed 1.7 MPa and should not be lower than 1.3 MPa, while the normal range for low pressure is generally not lower than 1.15 MPa and not higher than 1.25 MPa. Substance Introduction: R134a is the most widely used medium and low-temperature environmentally friendly refrigerant. It has excellent comprehensive performance, making it a very effective and safe alternative to dichlorodifluoromethane (CFC-12). It can be applied in most fields that use dichlorodifluoromethane refrigerant. Precautions: If the low pressure is higher or lower than this range, it indicates that the expansion valve adjustment is abnormal. Compressor issues are not included in this category. When the engine throttle is increased, the measured low pressure should decrease with the engine speed. The faster the speed, the more (faster) the pressure drops. This indicates good compressor performance; otherwise, it suggests a compressor malfunction.
I just went to the auto repair shop to recharge the refrigerant for my car, and the mechanic taught me how to read the pressure gauge. Normally, the low-pressure side should be between 1.5 to 2.5 bar, and the high-pressure side between 10 to 20 bar. But these values can vary with the weather—higher pressure on hot days and lower on cold days. Remember to measure with the engine running, AC on max cooling at highest fan speed for accurate readings. If both high and low pressures are too high, it might indicate too much refrigerant or poor heat dissipation. If both are too low, it's likely a refrigerant leak. If only one side is abnormal, the expansion valve might be clogged. Measuring pressure is quite technical, so it's better to rely on professional equipment for accurate diagnostics.
Last time I messed with the AC pressure myself, it really confused me. I had to look up a lot of information to figure it out. For R134a refrigerant under normal weather conditions, the low-pressure gauge should read around 0.15 to 0.25 MPa, and the high-pressure gauge between 1.0 to 2.0 MPa is considered normal. The worst scenario is when the high and low pressures are close, which usually indicates the compressor might be failing. I recommend testing in the cool morning for more accurate readings. Let the car idle for ten minutes to allow the AC system to circulate before measuring. If the pressure fluctuates wildly, it's likely there's air or moisture in the system, and you'll need to evacuate and recharge it.
