Q: Cooling fan is always on - 2002 Mercedes Benz SLK320

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As soon as I turn on my car the engine cooling fan starts to run, and it never turns off until I turn off the car. And when I start my car after it’s sat all night in the garage or even longer the cooling fan will come on as soon as I start my car. Do you have any idea why this happens? How can I fix this?

Hello. Though there are a lot of possible causes of this, the most common is a relay issue. If the relay for the fan is failing, then this will occur. It may also be something, such as a short in the control wire for the relay or a problem with the computer. I usually also check to see if the AC is staying on, which typically means that the issue is in the AC system. If you weren’t planning on fixing this yourself, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the AC system and let you know how this should be addressed.

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