What Causes the Low-Pressure Gauge of a Car's Air Conditioning System to Swing Back and Forth?
2 Answers
The low-pressure gauge of a car's air conditioning system swings back and forth due to excessive pressure in the system, causing the safety valve to release water; the safety valve is not fully closed; or water leakage caused by dirty water quality, blockages, or damage. Regarding the maintenance of the car's air conditioning system, here are some tips: Assessing Performance: Determining whether the air conditioning system is functioning properly is quite simple. If you notice poor cooling, weak airflow, or no cooling at all, you should check whether each component is operating normally and whether there is a lack of refrigerant. The refrigerant must be added according to the type specified in the vehicle's manual. These tasks can be handled at a professional service center. Regularly Replacing the Air Filter: For car owners, it is important to regularly replace the air conditioning filter. Generally, when driving in urban conditions, the air filter should be replaced every 3,000 kilometers or so. This not only keeps the intake system cleaner but also prevents a decline in cooling capacity due to a clogged air filter.
I've been repairing cars for over 20 years, and the fluctuating low-pressure gauge on the AC system is indeed a headache. This typically indicates unstable pressure in the refrigeration system, with common causes including insufficient refrigerant: if there's not enough refrigerant, the pressure will fluctuate dramatically when the compressor is running, causing the gauge needle to swing back and forth. Another possibility is moisture entering the system, where water condenses and evaporates at the expansion valve, leading to erratic pressure changes. Expansion valve failure is also quite common—if the valve is slow to open or close or gets stuck, it disrupts refrigerant flow. Improper engagement of the compressor clutch can also cause fluctuations because rapid load changes make it hard to stabilize pressure. Poor heat dissipation due to a clogged condenser can worsen the issue. My usual approach is to first check the refrigerant level: use a pressure gauge to measure whether the high and low pressures are within the normal range. If low, top it up but ensure there are no leaks. If the gauge continues to fluctuate, the expansion valve or dryer might be faulty and need replacement. Don’t ignore it—prolonged issues can damage the compressor, leading to costlier repairs. Regular maintenance, such as cleaning the AC filter and condenser, can help prevent these minor faults.
