Hello, I had an issue with my W204 (2008) 119,812 miles on the clock. Each time I started the car the engine after ~10 seconds the engine fan would start spinning at a high rate and even when I switched the car off it would continue for several moments before stopping. This happened regardless of whether the car was idle or even if I didn't use the heater or A/C. As part of the service I had done on the car when it reached 100,000 it included: Transmission & Gearbox Service Coolant Change New Sparkplugs Re-Gas A/C System I took it to my local indie who does my servicing and all he could diagnose was that the fan was not at fault. He could vary the fan speed and suggested it could be a rather serious matter of the ECU. However before proceeding down that route it would be best to take it to a Mercedes garage for a diagnostic service. I did realise after my indie's attempts to pinpoint the problem the AC wasn't actually working, only lukewarm air was spat out. Regardless whether I turned on the heater or AC on the engine fan could continue to spin like a turbine. Anyway, Mercedes confirmed it was the A/C Temperature Sensor was at fault, the part cost £44.30 and labour was £212.50. Compared to the potential cost of a new ECU I'm glad to say I can keep the car on the road. I hope this helps someone who comes across a similar issue as many posts point out as ECU the likely culprit.