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Cooling Fan Sensor Replacement
 
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Pelican Technical Article:

Cooling Fan Sensor Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$45 to $60

Talent:

*

Tools:

22mm wrench

Applicable Models:

BMW E10 2002 Coupe/Conv (1967-76)
BMW E21 320i Coupe (1977-83)

Parts Required:

Sensor

Hot Tip:

Work on a cold cooling system

Performance Gain:

Proper working fan

Complementary Modification:

Flush cooling system

Not all BMW 2002s come with a cooling fan sensor but if your vehicle does it is easy and quick to replace. The sensor uses the coolant temperature to turn the fan on for additional cooling. It is a simple open loop switch that closes when the coolant reaches a certain temperature; the closing of the switch allows the current to flow and tells the fan to turn on. If your fan is not turning on or never turning off there is a good chance your cooling fan switch has failed.

The sensor is located on the top of the motor on the coolant pipe that comes out of the head. It is at a high point in the cooling system so you can change it out without a lot of coolant loss. Just make sure you perform the work while the system is cold and NOT under pressure.

NOTE: For BMW 320I E21, the cooling fan (aux fan) temp switch is located on the bottom left of the radiator (unlike the the 2002 M10 engine where it is located on the coolant neck).

The sensor is located on the top of the motor on the coolant pipe that comes out of the head.
Figure 1

The sensor is located on the top of the motor on the coolant pipe that comes out of the head. It is at a high point in the cooling system so you can change it out without a lot of coolant loss. Just make sure you perform the work while the system is cold and NOT under pressure.

The coolant pipe from the head contains both the cooling fan sensor (red arrow) and the temperature sensor (yellow arrow).
Figure 2

The coolant pipe from the head contains both the cooling fan sensor (red arrow) and the temperature sensor (yellow arrow). The fan sensor is to the left of the temperature switch and has two prongs, while the temperature sensor only has one.

On simple open/close sensors like this it does not matter which wire goes on which prong.
Figure 3

On simple open/close sensors like this it does not matter which wire goes on which prong. Just make sure you are not stretching them when reinstalling.

Due to the location and height of the sensor in the cooling system you can replace this sensor without a lot of loss of coolant.
Figure 4

Due to the location and height of the sensor in the cooling system you can replace this sensor without a lot of loss of coolant. We are working on the Clarion Build's BMW 2002 with a fully restored engine. We performed the work without draining the system. Just make sure the coolant and engine are cold and there is no pressure in the system. Some coolant may escape so be prepared to catch it with a shop rag. Use a 22mm wrench and remove the sensor.

When installing the new sensor make sure it has a new crush washer.
Figure 5

When installing the new sensor make sure it has a new crush washer. You are installing the sensor with an aluminum crush washer on an aluminum pipe so you do not need to over tighten this when installing. Installation is the reverse of removal. There will be a small air bubble that will move through the system. If you have any concerns you can follow the instructions on how to bleed the coolant system by referring to the coolant flush and fill article.

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Page last updated: Sat 2/25/2017 02:59:26 AM