Why is the air conditioning pipe outside the car very cold but not cold inside?
3 Answers
It may be due to insufficient refrigerant or a dirty air filter. Below are the relevant explanations: 1. Refrigerant: Refrigerant, also known as coolant or freon, is the medium substance used in various heat engines to facilitate energy conversion. 2. Function of the air filter: It ensures the air filter fits tightly against the housing, preventing unfiltered air from entering the cabin; it separates solid impurities such as dust, pollen, and abrasive particles from the air; it adsorbs moisture, soot, ozone, odors, carbon oxides, SO2, CO2, etc., from the air; it prevents car windows from fogging up, ensuring clear visibility and safe driving for passengers; it provides fresh air for passengers, preventing them from inhaling harmful gases and ensuring driving safety; it effectively sterilizes and deodorizes.
After driving for so many years, I've found that it's quite common for the car's AC outer pipes to be cold while the interior doesn't cool down. The main reason usually comes down to insufficient refrigerant or a leak. The outer pipes feel cold because the compressor and condenser are running, with refrigerant flowing through them, but if the interior isn't cooling, that's odd. It could also be an issue with the expansion valve or dryer—if they're clogged or broken, refrigerant can't reach the evaporator to cool properly. Another possible cause is the evaporator itself icing up or malfunctioning, especially if the fan or blower is weak, preventing proper airflow. If the AC system hasn't been serviced for too long, low refrigerant levels can cause this. I recommend checking the refrigerant level first—use a pressure gauge to test it. If it's too low, you'll need to top it up or check for leaks. Also, a dirty cabin air filter can block airflow—replacing it might solve part of the problem. In any case, don't rush to DIY; take it to a proper shop and let the professionals handle it to avoid turning a small issue into a big one.
As a car owner, I've encountered this issue too. Just last week, I had my car repaired. The AC outer pipe was icy cold, but the cabin wasn't cooling properly. The cause was either refrigerant leakage or an expansion valve malfunction. A cold outer pipe indicates the system is functioning, but insufficient internal cooling is often related to low evaporator efficiency. Issues like dust buildup on fan blades or seized bearings can reduce airflow, leading to poor heat exchange in the evaporator and inadequate cooling. Compressor pressure instability can also cause problems—even with a cold outer pipe, insufficient compression affects overall performance. I tried checking fuses and pipes myself but found nothing conclusive. Eventually, a professional technician diagnosed a faulty dryer. Remember, don't delay repairs—driving without AC in hot weather risks heatstroke and safety hazards. Regular maintenance, like periodic refrigerant top-ups, can prevent many such issues.
