BMW 840i Radiator Fan Assembly Replacement Cost

Remember to be safe when dealing with any electrical system or spinning fan blades. The radiator fan should be checked to make sure it is not damaged or obstructed. An electric radiator fan can be connected to a power supply with the correct voltage (typically around 12 volts) to force it to turn on. If the fan doesn't spin with external power being supplied, then the entire fan assembly or at least the motor should be replaced. A radiator fan typically turns on when a specific coolant temperature is reached or if the air conditioning system is turned on. If the fan motor works with a different power source, but doesn't turn on with the air conditioning, at a specific engine temperature, or with another known condition that should start the fan, then the sensors in those systems responsible for sending the signal to turn the fan on should be checked and replaced. The radiator fan's electrical system including relays, fuses, and wiring should also be checked. If your vehicle is equipped with a mechanical radiator fan, then most likely only the fan clutch needs to be checked and replaced.

The radiator fan slides out easily on most vehicles. The battery will be disconnected, then the fan connector will be unplugged, and retaining hardware for the upper fan will be removed. Some plastic guards will need to be removed from the undercarriage of the vehicle in order to access any retaining hardware.

There are many universal radiator cooling fans available for purchase, but they may not be reliable. It's best to purchase the fan made specifically for the vehicle.

To properly diagnose the fan, you'll need some knowledge of electrical circuits, and you'll need to know when it's supposed to run. If you can confirm it's faulty, it's often pretty easy to replace as a DIY project.