Me, as an owner of a Mercedes B-Class in the UAE, I can tell you the fan running at high speed constantly is almost always a sign of a struggling cooling system, and here, the heat is your main enemy. The most likely culprit is a faulty coolant temperature sensor. In our summer temperatures that regularly hit 45°C, this small electronic component gets overworked. When it fails, it sends incorrect "overheating" signals to the car's computer, which in turn commands the fan to run at full blast non-stop to try and cool an engine that might actually be at a normal temperature.
Based on common issues faced by GCC-spec vehicles and discussions with specialist workshops in Dubai, other local factors to check include:
- Clogged Radiator: Dust and fine sand from our roads and construction sites can block the radiator's fins, drastically reducing its cooling efficiency. The fan then has to work harder to pull air through.
- Aging A/C Condenser Fan: The electric fan for the air conditioning condenser works in tandem with the main cooling fan. If the A/C fan is weak or failing, especially when the A/C is on maximum during a desert drive, the main fan compensates by running at high speed.
- Low Coolant Level or Wrong Mixture: A slow leak or using the incorrect coolant/water ratio for our climate can lead to higher operating temperatures. For the UAE, a minimum 40% antifreeze concentration is recommended for its higher boiling point and corrosion protection against hard water.
Ignoring this in the UAE can be costly. A constantly running fan drains the battery, especially during short trips. More critically, if the issue is a real overheating problem (like a stuck thermostat or water pump failure), continued driving can lead to severe engine damage. The most reliable first step is an OBD-II scan at a garage with Mercedes-specific diagnostic tools to read the exact fault codes. For a B200 commonly used here, replacing a faulty coolant temperature sensor typically costs between AED 300-500 including part and labor at an independent specialist. Addressing a clogged radiator through professional cleaning can cost around AED 150-250 and often provides immediate improvement. A professional diagnostic scan is the most cost-effective first step. Clearing a dusty radiator is a quick and often effective fix. Ignoring a fan that runs constantly can lead to a major engine repair bill.
