Car Fan Still On After Engine Off

Causes

There are several possible causes for the car fan to stay on after the engine is turned off:

• Coolant temperature sensor failure. The coolant temperature sensor is responsible for sending a signal to the engine’s computer (ECU) indicating the temperature of the coolant. If this sensor fails, the ECU may think that the engine is still running and keep the fan on.
• Fan relay failure. The fan relay is responsible for turning the fan on and off. If this relay fails, the fan may stay on even when the engine is off.
• Wiring issue. A wiring issue can also cause the fan to stay on after the engine is off. This could be a problem with the wiring between the ECU and the fan, or between the fan and the battery.

Diagnosis

To diagnose the cause of the car fan staying on after the engine is off, you will need to:

1. Check the coolant temperature sensor. Disconnect the electrical connector from the coolant temperature sensor and measure the resistance between the two terminals with a multimeter. The resistance should change as the coolant temperature changes. If the resistance does not change, or if the resistance is very high or very low, the sensor is likely faulty and will need to be replaced.
2. Check the fan relay. Remove the fan relay from its socket and check the terminals for any signs of damage or corrosion. If the terminals are damaged or corroded, the relay will need to be replaced.
3. Check the wiring. Inspect the wiring between the ECU and the fan, and between the fan and the battery, for any signs of damage or corrosion. If you find any damaged wires, they will need to be repaired or replaced.

Repair

Once you have diagnosed the cause of the car fan staying on after the engine is off, you will need to repair the problem. This may involve replacing the coolant temperature sensor, the fan relay, or the wiring.

If you are not comfortable performing these repairs yourself, you should take your car to a mechanic to have them done.

Additional Information

In some cases, it is normal for the car fan to stay on for a short period of time after the engine is turned off. This is especially true if the engine has been running at high temperatures. The fan will help to cool the engine down and prevent it from overheating.

However, if the car fan stays on for more than a few minutes after the engine is turned off, it is likely that there is a problem that needs to be fixed.