97BMW 318i fan runs and drains battery when car is off

depending on the engine temperature the fan is supposed to remain on after you turn the engine off, until the engine reaches a preset cooler temperature. when it reaches cooler temperature usually within 5 minutes or so it should cut off... if you cut it off and it is running 30 minutes later.. then there is a problem with the fan relay or temperature sending unit.

fans are designed to run on after you shut engine down as engine temperature rise after switching off . running hot could be caused by the top hose having gone soft when you rev the engine the water pump sucks the hose flat stopping the coolant flow or the radiator is blocked and need flushing out

it could be a faulty fan relay, however some of these had a continue run time program that allowed the motor to cool off after engine shut down. it shouldn`t run longer than about 2/3 minutes.

The fan runs for a short time, after ignition off, to continue to cool the hot engine.

Many cars have this feature. The fan will run for a few minutes at a time until the coolant in the radiator drops below a certain temperature. Most vehicles with this feature will have a warning label on the radiator shroud indicating that the fan may start without warning when the engine or radiator is still hot. The only time you would need to be concerned would be if the fan continues to run without turning itself off, and causing the battery to be drained.

well the electric fan will turn on and off at any time. when you stop your vehicle and the fan continues to run what is happening is the temp sensor says the motor is still too hot and it needs more cooling. now as it reaches the cooling temp it is also suppose to shut it down. have the sensors checked.

This is perfectly natural for the fan to continue running when the motor is turned off. I have seen them run for up to 15 minutes depending on how hot the day and the engine are. If it is not cutting off at all then you may have a problem in your heat sensor.

It would be normal for the cooling fans to run after you shut the car off because the power to the fans is turned on and off by a thermostat and not the key. Don't worry about it unless it runs for more than 15-20 minutes when you shut the car off. It may run that long in summer if the car is hot but less in the winter. Hope this helps.

Having the fan run on for a bit after the engine has stopped is not abnormal in itself, but 20 minutes sounds excessive.

If the fan does eventually shut off, I'd consider changing the thermoswitch (this is a sensor screwed into the radiator somewhere near the bottom, with a pair of wires connected to it - to change it, you'll need to drain the cooling system).

If the fan stays on continuously until the battery is completely flat, see what happens when you unplug the wires from the thermoswitch. If this stops the fan, you need to replace the thermoswitch. If it doesn't, then you need to examine the wiring associated with the switch and the fan, looking for damaged insulation.

A.