Why Is My Car Fan Still Running When Turned Off?

January 25, 2024

A car’s engine fan is designed to cool the internal engine by drawing air through the radiator. This allows the coolant to dissipate heat from the engine while it is running and is a critical component in keeping your engine at an optimal temperature to prevent overheating. However, the cooling system may not always work properly. This can lead to the fan staying on even after you turn off the ignition. This is often the result of a faulty fan relay or electrical issues.

It’s also possible the problem is caused by a low coolant level or another issue with the heating and cooling system. But it’s unlikely that the cooling fan will stay on for hours at a time as it is usually controlled by a thermostatic switch.

This is controlled by the PCM (powertrain control module) and the ECU (electronic control unit) which get signals from sensors like the engine temperature sensor and A/C inputs. When this sensor reaches a certain level, the ECU or PCM tells the fan relay to switch on.

If the cooling fan does turn on, it’s important to note that it will remain on for only a few minutes. It will then shut off once it gets the signal to stop from the ECU or PCM. However, if it continues to run for longer than this then the battery will be drained and this is a big problem that needs to be fixed as soon as possible.


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