What Causes the Mercedes-Benz AC to Not Cool When Turned On?
3 Answers
Insufficient refrigerant, leaks in the pipeline, or a damaged refrigerant pressure sensor can all cause the Mercedes-Benz AC to not cool when the AC is turned on. The specific reasons are as follows: 1. Damaged air conditioning flap. Damage to the air conditioning flap is relatively rare. It is located in the middle-lower part of the dashboard. If it is damaged, it can only be replaced, though replacement is very complicated. 2. Dirty condenser. When the condenser is dirty, the AC's heat dissipation becomes poor, leading to reduced cooling efficiency. Therefore, regular cleaning is necessary. 3. Damaged AC compressor, throttle valve, or expansion valve. The AC compressor is not easily damaged, but malfunctions in the throttle valve or expansion valve can cause poor AC performance. Diagnosing this issue is very troublesome and requires a visit to a 4S shop for repair. 4. Aged or loose compressor drive belt. The refrigerant relies on the moving parts driven by the AC compressor. A loose drive belt can cause the compressor to slip, so when the AC is not working properly, the engine belt should be checked.
If the AC is not cooling, I guess it might be a refrigerant leak or a faulty compressor in your Mercedes. Last time my car had the same issue—it was unbearably hot in summer, and it turned out the condenser was clogged with too much dirt, affecting heat dissipation. If the fan isn’t spinning or is running too slowly, the AC system can’t cool properly. Or, if the temperature sensor is broken and sending wrong signals, the compressor won’t start. Electrical issues like blown fuses or relay failures are also common problems. During inspection, you can check by feeling if the AC pipes are overheating or listening for abnormal sounds from the fan and compressor. For regular maintenance, it’s recommended to clean the AC filter and check refrigerant pressure periodically. Generally, you should recharge the refrigerant every two to three years, as aging systems leak quickly. For repairs, it’s best to visit a 4S shop for professional diagnostics to avoid DIY mishaps.
My Mercedes-Benz also had the issue of the AC not cooling properly before. After checking for a long time, it turned out the compressor was faulty and not running. I remember sweating a lot while driving in the summer, initially thinking it was due to the high outside temperature. Later, the mechanic said insufficient refrigerant or leaks could also cause this—if the system pressure is too low, it won’t cool. If the fan isn’t working or running at low speed, the heat dissipation is poor, and the AC naturally underperforms. Electrical issues like loose wiring or control module failures are also common causes. Mercedes has many electronic systems, and sensor misreporting can trigger problems. I suggest doing a quick check yourself first: when the AC is on, feel the air vents—if there’s no cold air at all, it might be a major issue. Or check if the condenser fins in front of the radiator are clogged with dust. It’s good practice to park in the shade and inspect the AC system seasonally to reduce the chance of malfunctions. Addressing issues promptly is crucial, as hot weather can easily lead to dangerous driver fatigue.
