Why is the high-pressure pipe of the car air conditioning cold while the low-pressure pipe is not cold?
2 Answers
When the high-pressure pipe of the car air conditioning is cold while the low-pressure pipe is not, it indicates that the compressor is damaged. Under normal working conditions, the low-pressure pipe should be cold, and the high-pressure pipe should be hot to the touch. If the high-pressure pipe is cold, it means the compressor is faulty and needs to be replaced. The air conditioning working process: Compression process: The compressor sucks in the low-temperature, low-pressure refrigerant gas from the evaporator outlet and compresses it into high-temperature, high-pressure gas, which is then discharged from the compressor. Heat dissipation process: The high-temperature, high-pressure superheated refrigerant gas enters the condenser. Due to the decrease in pressure and temperature, the refrigerant gas condenses into a liquid, releasing a large amount of heat. Throttling process: The higher-temperature and higher-pressure refrigerant liquid passes through the expansion device, where its volume increases, and the pressure and temperature drop sharply, exiting the expansion device in a mist form (fine liquid droplets).
The other day I noticed something wrong with my car's AC - the high-pressure line felt icy cold, but the low-pressure line wasn't cool at all. After checking, I learned there are three common causes for this. The refrigerant might have leaked to critically low levels, causing insufficient system pressure that disrupts the circulation. If the expansion valve gets stuck in the open position, the refrigerant can't properly expand and absorb heat in the low-pressure side, leaving the lines warm. When the compressor wears out or its electromagnetic clutch fails, it can't build sufficient high pressure, paralyzing the entire system. I've encountered this situation before - it turned out to be a clogged filter screen in the receiver-drier restricting refrigerant flow. Malfunctioning AC significantly impacts summer driving comfort. Abnormal high-pressure line temperatures require immediate professional inspection and repair to prevent compressor burnout and more extensive damage.
