What Causes a Mercedes-Benz AC to Not Cool When Turned On?
3 Answers
When a Mercedes-Benz AC is turned on but fails to cool, it could be due to insufficient refrigerant, leaks in the pipeline, or a faulty refrigerant pressure sensor. The specific reasons are as follows: Damaged Air Conditioning Flap: A damaged air conditioning flap is relatively rare. Located in the middle-lower part of the dashboard, if it is damaged, it must be replaced, though the replacement process is quite complicated. Dirty Condenser: When the condenser is too dirty, the AC's heat dissipation deteriorates, leading to poor cooling performance. Therefore, regular cleaning is necessary. 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 complex and requires a visit to a 4S shop for repair. Additionally, if the compressor drive belt is aged or loose, the refrigerant circulation—which relies on the compressor's moving parts—may be affected. A loose drive belt can cause the compressor to slip, so if the AC is not working properly, the engine belt should also be inspected.
I also experienced the awkward situation of the AC not cooling when driving my Mercedes. It happened during a summer traffic jam, and the AC only blew hot air, almost causing heatstroke. After checking, the most common reasons include insufficient refrigerant, possibly due to a leak, such as loose pipe connections or a damaged condenser; the compressor can sometimes fail, especially if it's not maintained regularly, leading to seizing; or the air filter is too dirty and blocks ventilation, or electrical components like the temperature control sensor are faulty, causing the system to misjudge the temperature and not start cooling. I first replaced the filter myself, but it still didn’t work. Later, at the shop, I found out the refrigerant had completely leaked. My advice is not to delay when facing this issue—promptly check for leaks or top up the refrigerant. Otherwise, not only will it disrupt your trip, but it may also worsen the damage. Regularly cleaning the condenser and replacing the filter annually can greatly prevent such problems.
Hey, I love tinkering with cars and have done quite a bit of research on Mercedes' AC not cooling. Simply put, the issue might lie in a few key areas: insufficient refrigerant is the most common cause, either due to leaks or improper system charging; if the compressor fails, a loose belt or internal wear can prevent it from turning; if the condenser is dirty or damaged by stones, poor heat dissipation affects cooling; and small components like relays or sensors failing can cause the ECU to miscontrol. I've tried using an OBD scanner to check for trouble codes, which can sometimes pinpoint the issue, but I recommend first checking fuses and filters—these are simpler. If that doesn't work, professional testing of compressor pressure is needed to avoid wasted effort. Using recirculation mode more often and minimizing dust buildup can extend the AC's lifespan.
