What Causes the Air Conditioning Not to Cool at Vehicle Idle?
3 Answers
The reasons why the air conditioning does not cool at vehicle idle are: 1. The expansion valve is damaged, preventing the formation of high pressure in the system before the expansion valve, and the high-pressure refrigerant cannot reach the pressure of 150Kpa, which causes the evaporator behind the expansion valve to fail to cool down; 2. Internal wear of the air conditioning compressor, resulting in the pressure between the air conditioning compressor and the expansion valve not reaching 150kpa to 200Kpa, causing the refrigerant in the system to not circulate normally. The solution to the air conditioning not cooling at vehicle idle is: add refrigerant along with fluorescent dye, after using the vehicle for a period of time, inspect the air conditioning system with a dedicated fluorescent lamp. If there is a leak point, it will glow, and the leaking parts and components can be repaired or replaced.
I was also puzzled when I first encountered this issue—the AC blowing hot air at idle is really uncomfortable. The main reason is that the AC compressor relies on the engine to drive it, and at idle, the RPM isn't enough to properly compress the refrigerant. The most common issue is the condenser being clogged with dust or pollen, or the space between the radiator and condenser filled with debris, leading to terrible heat dissipation. A loose or worn-out compressor belt causing slippage is also common—last time, my car had a squeaky belt that led to insufficient cooling. Another headache is refrigerant leakage; aging seals on pipe connections can cause slow leaks. One detail many overlook: if the cooling fan is stuck or not spinning fast enough, poor heat dissipation will cause the AC system to fail. Don’t tinker blindly—just head to the repair shop and have them check the system’s high and low pressures with a gauge for the most reliable diagnosis.
I'm all too familiar with air conditioning not cooling properly—just helped a neighbor fix this issue last week. When idling, the AC system's energy supply is limited, so focus on checking heat dissipation components. The most common culprit is the fan not spinning, which could be caused by a burnt relay or worn motor brushes. Blocked radiator grilles are another classic issue—using a high-pressure washer to clean the condenser during car washing can solve 80% of the problem. If the compressor clutch isn't engaging properly, you'll hear a clicking noise, and insufficient lubrication in the bearings can also affect power transmission. Here's a lesser-known tip: if the expansion valve is clogged, the high-pressure pipe will frost over, and in this case, the entire valve assembly must be replaced. There's also a professional diagnostic method—connect to the diagnostic computer and check the AC pressure sensor data stream; abnormal values will immediately reveal the issue.
