What Causes the Car AC to Not Cool at Idle Speed?
2 Answers
When the car AC fails to cool at idle speed, the first issue we consider is belt slippage. Since the AC compressor is driven by the crankshaft via a belt, when the belt slips, the efficiency of the AC compressor decreases. The most noticeable effect is poor cooling performance when the engine is idling or running at low speeds, with cooling gradually improving only when the accelerator is pressed and the engine speed increases. Additional possible causes: 1. Another reason could be a lack of refrigerant. Car AC systems typically require refrigerant recharge every 2-3 years, and some cars may need it annually. Even with a tightly sealed AC system, refrigerant can still escape, especially if there are minor leaks in the AC lines or condenser. 2. The main causes of belt slippage include a loose, aged, or severely worn belt, or insufficient tension from the tensioner pulley. The solution is straightforward: replace the belt.
I encountered this issue when repairing my car the other day. There are quite a few reasons why the AC doesn't cool at idle. The most common one is the cooling fan not spinning, especially when idling in traffic. The engine speed is low, the fan speed is slow, and the cooling efficiency is poor, so the compressor automatically shuts down. Another possibility is low refrigerant levels due to leaks, leading to insufficient cooling circulation. Another issue could be a loose or worn belt, causing the fan to fail to spin. I've personally seen a customer's car blowing hot air in traffic because the fan blades were stuck with dirt. I recommend opening the engine hood to check if the fan is spinning. If it's spinning slowly, take it to a professional shop to clean the condenser and recharge the refrigerant. Don't delay—safety comes first when driving in hot weather, or else a burnt compressor will cost even more to repair. Regular maintenance keeps the AC durable and makes your journeys more comfortable.
