Car Fan Still On When Engine is Turned Off

You park your car, turn off the ignition and start walking away. Then you notice the engine cooling fan is still running even though the car is turned off. 

It is ok for the engine cooling fan to keep running for a few minutes after turning off the car. Your car fan will run for a few minutes after you turn off the car then turn off.  

This is normal in many vehicles, such as BMW or Mercedes-Benz. The radiator fan may run up to five minutes and sometimes longer.

Unless there is an electrical issue, it may stay on all the time until it drains the battery. 

When the engine is running, the coolant circulates from the engine and flows to the radiator, where heat is dissipated. When the engine is turned off, the coolant doesn't circulate, and the heat stays trapped, therefore prolonging the engine from cooling. Running cooling fans help cool down the engine even after you turn off the car. 

Common Causes

If your cooling fan runs for over 10 minutes after turning off the engine, you may have a problem that needs to be fixed.

Here are some possibilities causing the fan to stay running longer.

  • low coolant level,
  • faulty coolant temperature sensor,
  • PCM or ECU defective
  • coolant leaks from the water pump,
  • cracked radiator,
  • worn upper or lower radiator hoses,
  • leaky heater core,
  • leaky thermostat housing,
  • rusted coolant bypass pipe,
  • bad radiator fan relay,
  • short in the electrical wires and so on. 

What should I do if the engine fan never turns off? 

disconnect negative battery terminal to turn off a cooling fan staying on

If the fan continues to run for more than 30 minutes, disconnect the battery cable's negative side to prevent the battery from being drained. 

Troubleshooting Tips

Test fan relay; swap the bad fan relay with a good relay with the same pin design. Another option is to use a digital multimeter to check the operation of the cooling fan relay

If the fan turns off, that means the relay is at fault.

Furthermore, check for low coolant level and possible leaks that may be causing it. Usually, a low coolant will equate to a hotter engine. Therefore, it will activate the fan more often.  

By  YOUCANIC Automotive Experts

Published on: Thursday, December 12, 2019.
Updated on: Saturday, November 14, 2020