Loud Engine Fan (W204)

[signeddesign]

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.

 

[Slaurro]

Hello! I`m having a similar problem on my C250 CDI. The fan kicks in after i start the car and it's very noisy. It happens even with the A/C turned off. This just started happening today. The A/C also stopped working, when i turn it on it blows hot air even when i set it to minimum. Weird thing is, if i turn the a/c off and only leave the eco blower on, the air is cooler than with a/c on.
I'm thinking i might have the same problem as you did, the temp sensor. Can you please tell me, was it the interior cabin temperature sensor or is there an a/c temp sensor in the engine compartment? Do you happen to have a link or a part serial number? I don't know what to order. It would be of great help. Thanks!

 

[Auto-mobile]

Sits in the bottom of the condenser, you need to check the value the sensor is showing on a diagnostic machine to confirm if it's faulty, if it needs a sensor it will need a regal to.

Common problem.

 

[Slaurro]

Are you by any chance referring to this sensor on the evaporator? I understand it's located in the center console, behind the small round hole. I guess I'll go get a star diagnostic... or is it possible to get the temperature reading on universal testers as well?