Why is the high-pressure pipe of the car air conditioner not hot?
4 Answers
Reasons why the high-pressure pipe of the car air conditioner is not hot: Insufficient refrigerant in the air conditioner; Excessive opening of the expansion valve; The compressor is not working or the compressor is faulty. Below is some information about car air conditioners: Automatic air conditioner: The electronic control unit will operate the air conditioning system automatically based on the settings made by the driver or passengers via the buttons on the air conditioning display control panel. It will adjust the air supply temperature and speed in a timely manner according to the signals input by various sensors to maintain the optimal air environment inside the car. Traditional air conditioner: It is manually controlled. There is a temperature adjustment knob on the air conditioning control panel, and rotating it can change the set temperature.
I've been driving for many years, and the high-pressure pipe should be hot when using the air conditioning in summer. If it's not hot, there's likely an issue with the AC. Common causes include insufficient refrigerant, possibly due to a leak, or a faulty compressor. I remember one time the high-pressure pipe was ice-cold, and upon inspection, it turned out the fan wasn't running, leading to insufficient cooling, which caused the low pressure to be too high and the high pressure not to heat up. A clogged expansion valve could also restrict refrigerant flow. I recommend first checking the AC pressure to see if the high and low pressures are balanced normally. If the gauge readings are low, try topping up the refrigerant. A cold high-pressure pipe affects cooling efficiency, making driving uncomfortably hot and even leading to unsafe drowsy driving. It's best to visit a repair shop early to prevent cascading failures. Regular maintenance of the AC system, including cleaning the condenser and checking the pipes, can help avoid such issues.
As someone who frequently tinkers with cars, if the AC high-pressure line isn't hot, I'd first check the refrigerant level. Use charging hoses to measure high and low side pressures - if the low side is high while the high side is low, there might be a leak in the system. Next, inspect whether the compressor belt is loose or worn, or if the electromagnetic clutch isn't engaging. Expansion valve issues are also common - I've personally tried using cleaning agents to deal with blockages. A dirty condenser or faulty fan can cause poor heat dissipation. Be careful not to randomly disassemble the high-pressure line as the system operates under high pressure which can be dangerous. Troubleshoot step by step starting with simple checks: first examine fuses and relays, then test circuit current. If you're not familiar, don't mess with it - know when to call professional help. A cold high-pressure line indicates the AC isn't working, so address it early to prevent complete AC failure.
Driving for a long time gives you some knowledge about air conditioning. If the high-pressure pipe is not hot, it could be due to low refrigerant or compressor failure. Check the pressure gauge readings—if the high and low pressures are unbalanced, insufficient system pressure can cause the pipes to cool. A blocked expansion valve can hinder refrigerant flow, or a non-functioning fan can affect heat dissipation. It could also be a control system error, such as a sensor misreporting the temperature. Measuring the refrigerant charge is the simplest step; if the pressure is normal but the high-pressure pipe is cool, consider component failure. Repair it early to avoid increased costs, such as the higher expense of replacing a damaged compressor. Don’t ignore this phenomenon while driving safely.
