What Causes High Low Pressure and Normal High Pressure in Car Air Conditioning?
3 Answers
When the car air conditioning exhibits low low pressure and normal high pressure, it is highly likely due to a malfunction or damage in the air conditioning expansion valve. Solution: The solution for high low pressure and normal high pressure in car air conditioning is quite simple. Just remove the air conditioning expansion valve and check if it is functioning properly. If it is indeed faulty or damaged, simply replace it. More details are as follows: 1. Note: Since the expansion valve of the car air conditioning system is located on the firewall side of the vehicle, it is quite inconvenient to remove. Additionally, temporary recovery of the air conditioning refrigerant is required, which involves a significant amount of work. Therefore, it is recommended to go to a 4S shop for this task, as attempting to do it yourself may be counterproductive. 2. Normal working pressures of air conditioning high and low pressure: Under normal conditions, when the compressor is running at 1500-2000 rpm, the high pressure should be around 1.5-2.0 MPa, and the low pressure should be around 0.15-0.35 MPa.
If the low-pressure side of the car's air conditioning system shows excessively high pressure while the high-pressure side remains normal, this typically indicates an issue with the expansion valve. The expansion valve is a critical component that regulates refrigerant flow. If it opens too wide, excessive refrigerant enters the low-pressure line, causing abnormally high low-side pressure while the high-side pressure remains unchanged. This condition may also relate to insufficient refrigerant, such as air or moisture contamination in the system affecting normal circulation. When the expansion valve fails, the air blown by the AC becomes warm or insufficiently cool, leading to discomfort while driving. I recommend promptly inspecting the expansion valve's condition and using professional pressure gauges to measure system pressures, verifying whether values fall within normal ranges. Delayed repairs may cause compressor wear or system leakage, potentially leading to more severe failures or even breakdowns. During routine AC maintenance, pay attention to the expansion valve's sealing integrity and aging to minimize such issues.
As a frequent driver, I encountered an issue with high low-pressure in my car's air conditioning system last month. While driving, the cabin felt warm despite the fan blowing, and the cooling was weak. A friend suggested that the expansion valve might be opening too wide, causing excessive refrigerant flow. It's like leaving a faucet slightly open—refrigerant floods into the low-pressure side, raising its pressure while the high pressure remains unchanged. Another possibility was a slight refrigerant shortage, which, combined with air entering the system, made it unstable. You can do a simple check by feeling the high and low-pressure pipes—if the low-pressure pipe feels unusually warm, this is often the cause. I eventually went to a repair shop and replaced the expansion valve, which fixed the issue, and now the AC cools properly. It's important to avoid leaving the AC system exposed for too long to prevent dust from entering. If you notice the cooling isn't effective, early inspection is better than waiting for a major problem to develop.
