BMW Cars 1999-06

Electric Engine Fan

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Electric Fan Switch





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Fig. The dual range electric cooling fan switch threads into radiator-M50 engine shown

The electric cooling fan switch is installed into a coolant passage and operates the radiator auxiliary electric cooling fan when the coolant temperature reaches a specified temperature or when the air conditioner is activated. The fan has operates in two stages depending on the engine coolant temperature.


NOTE
If the air conditioner is in proper working order, the engine cooling fans will operate when the air conditioner is turned on, regardless of the coolant temperature. When testing the electric cooling fan switch, make sure the air conditioner is OFF.

Below the specified temperature the switch is off (open), and at or above the specified temperature, the switch is on (closed), and completes a series circuit that triggers the cooling fan relay allowing the cooling fan to operate.

Removal & Installation

The electric cooling fan switches are mounted on the side of the radiator into the cooling system passages.


WARNING
When removing a fan switch, make sure the coolant temperature is below 100°F (38°C).

  1. Note the radio security code and radio station presets.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Drain the coolant from the radiator drain petcock into a suitable and sealable container.
  6.  
  7. Locate the fan switch, then disconnect the wire terminal from the fan switch
  8.  
  9. Remove the switch using a sensor socket or box-end wrench.
  10.  

To install:

  1. Installation is the reverse of the removal procedure.
  2.  
  3. Reconnect the negative battery cable.
  4.  
  5. Top off coolant level and bleed the cooling system as necessary.
  6.  
  7. Enter the radio security code and radio presets.
  8.  

Testing

WARNING
Use care when testing the radiator cooling fans as the fan blades have sharp edges and with the vehicle's battery connected, the cooling fans could begin to operate without notice. Always keep hands, fingers, tools, clothing or other objects away from the cooling fans at all times. Failure to observe this warning could lead to personal and/or equipment damage.

The electric cooling fan switch is a double temperature heat sensitive on-off, switch consisting of three electrical terminals and is mounted into the side of the radiator. The switch is used to complete a ground circuit for the cooling fan relay. Depending on the engine coolant temperature and climate control settings, the cooling fan will operate at either high or low speed.

Because the fan switch is used to complete an electrical circuit, it is tested for continuity using an ohmmeter. The switch terminal positions, wire color and affected electrical circuits are as follows:



Terminal position 1: Brown wire, chassis ground
 
Terminal position 2: Black wire with green tracer, fan low speed circuit
 
Terminal position 3: Black wire with gray tracer, fan high speed circuit
 

The engine cooling fan switch remains in the open (off) position until the engine coolant reaches a certain temperature. The switch is designed to operate in two stages. Stage one operates the cooling fans at low speed by the switch completing the circuit between terminals 1 and 2. Stage two operates the cooling fans at high speed by the switch completing the circuit between terminals 1 and 3.

The temperature at which the switch achieves the closed (on) position for stage one (low speed) and stage two (high speed) varies from model to model and is determined by the actual temperature rating of the switch.

Switch Installed

CAUTION
Do not allow the engine to operate continuously without the aid of the auxiliary cooling fan otherwise severe engine damage may occur.

  1. Locate the cooling fan switch mounted on the radiator.
  2.  
  3. Detach the wire connector from the fan switch.
  4.  
  5. To test stage 1 of the fan switch, using a suitable ohmmeter or continuity tester check for continuity between the fan switch terminals 1 and 2.
  6.  
  7. Allow the engine to reach a coolant temperature as follows. The fan switch should have continuity (switch closed) at this temperature:

    Up to and including model year 1995: 194°F (90°C)
     
    1996-98 4-cylinder engines: 176°F (80°C)
     
    1996-98 6-cylinder engines: 196°F (91°C)
     

  8.  
  9. To test stage 2 of the fan switch, using a suitable ohmmeter or continuity tester check for continuity between the fan switch terminals 1 and 3.
  10.  
  11. Allow the engine to reach a coolant temperature as follows. The fan switch should have continuity (switch closed) at this temperature:

    Up to and including model year 1995: 210°F (99°C)
     
    1996-98 four cylinder engines: 190°F (88°C)
     
    1996-98 six cylinder engines: 210°F (99°C)
     

  12.  
  13. If the switch does not operate within the range of the supplied information, allow the engine to cool below 100°F (37°C) and replace the switch.
  14.  



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Fig. Squeeze the electrical connector to release the locking clip and carefully remove



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Fig. Use an ohmmeter to check the fan switch for continuity-M44 sensor shown

Switch Removed

WARNING
Submerging the electric cooling fan switch below the threads could damage the component. Perform this procedure in a safe and well-ventilated area. Wear eye protection and use care to not come in contact with any of the heated components. Do not use a heating device that produces an open flame.

Testing a radiator fan switch is not difficult, however to do so requires some basic equipment. To properly test the fan switch, the switch's probe must be submersed in heated water, only as far as the component's threads. The water must be heated while the temperature is monitored. When the water reaches the specified temperature, the fan switch should be closed. Use suitable fitting electrical jumper leads to avoid contact with the heated water during testing. Testing the switch requires the following equipment:



A safe source of heat, such as a portable electric hot plate
 
A container capable of being safely heated by a hot plate and handling heated water
 
A thermometer safely capable of reading 212°F (100°C)
 
A device to safely hold the switch such that only the coolant probe is submerged into the water
 
An ohmmeter or continuity tester
 

  1. Refer to the cooling fan switch removal and installation warning and procedures and remove the switch.
  2.  
  3. Attach a 12 inch wiring sub-harness to the cooling fan switch to avoid having to probe the switch while in the heated coolant. Place the switch into a suitable holding device such that the temperature probe of the switch is submersed in a container of heated water. Make sure the container can be safely heated using a suitable source of heat such as a portable electric hot plate.
  4.  
  5. Using a suitable thermometer to measure the coolant temperature, heat the water until the specified temperature is attained.
  6.  
  7. To test stage 1 of the fan switch, using a suitable ohmmeter or continuity tester check for continuity between the fan switch terminals 1 and 2. The cooling fan switch should have continuity (closed) between the electrical terminal positions 1 and 2 at the following temperatures:

    Up to and including model year 1995: 194°F (90°C)
     
    1996-98 four cylinder engines: 176°F (80°C)
     
    1996-98 six cylinder engines: 196°F (91°C)
     

  8.  
  9. To test stage 2 of the fan switch, using a suitable ohmmeter or continuity tester check for continuity between the fan switch terminals 1 and 3. The cooling fan switch should have continuity (closed) between the electrical terminal positions 1 and 3 at the following temperatures:

    Up to and including model year 1995: 210°F (99°C)
     
    1996-98 four cylinder engines: 190°F (88°C)
     
    1996-98 six cylinder engines: 210°F (99°C)
     

  10.  
  11. If the switch does not operate within the range of the supplied information, replace the switch.
  12.  



Click image to see an enlarged view

Fig. With the temperature probe of the fan switch submersed in heated water, an ohmmeter and a thermometer were used to check its operation

Testing




WARNING
Do not allow the engine to operate for a prolonged length of time without an operational cooling fan, otherwise, severe mechanical damage could occur.

The electric cooling fans can be tested by:



Simulating the cooling fan switch operation
 
Supplying power directly to the fan using a set of fused jumper leads
 

The advantage of testing the cooling fans by simulating the cooling fan switch operation is that this procedure tests the entire fan circuit.

The advantage of supplying power directly to the cooling fan is that this will quickly determine whether the fan motor itself is defective, or whether there is a problem with another component or the circuit wiring.

It is possible to have one or more problems. For example if a fan motor overheated or seized, the relay and/or wiring could be damaged. If the relay stuck in the closed position, the cooling fan could be damaged and the battery drained. If testing the fan circuit requires working near the cooling fan, disconnect the cooling fan and attach a test light to the cooling fan electrical connections. The will help to avoid the chance of being struck by the cooling fan. Also if testing for an intermittent condition, the test light can be monitored for an on/off condition much more easily than a cooling fan.

The cooling fan electrical connections are as follows:



Chassis ground: Brown wire
 
Power (High or Low speed): Blue, Black/Blue
 

The sensor wire electrical connections are as follows:



Chassis ground: Brown wire
 
Relay low speed trigger wire: Black/Green
 
Relay high speed trigger wire: Black/Gray
 

Proper testing should be done in an logical and organized method.

To check only the cooling fan proceed as follows:

  1. Check the battery voltage at the battery and at the fuse panel. The battery voltage should be at least 12.3 volts. If less than 12.3 volts, charge or replace the battery. The voltage measured at the fuse panel should be within 0.3 volts of the measured battery voltage, if not check the wiring for a poor connection between the battery and the fuse panel, and/or the battery and ground.
  2.  
  3. Make sure the ignition switch is in the OFF position.
  4.  
  5. Using at least a 12 gauge set of fused jumper leads proceed as follows:
    1. Detach the cooling fan electrical connection.
    2.  
    3. Connect the ground terminal of the jumper leads to a known good ground, or to the negative battery jump post and to the brown wire of the cooling fan.
    4.  
    5. Connect the positive terminal of the jumper leads to blue wire of the cooling fan.
    6.  
    7. Connect the other positive terminal of the jumper leads to the positive battery post. The fan should operate.
    8.  
    9. Disconnect the positive jumper lead from the jump post and move the positive jumper lead to the black/blue wire of the cooling fan.
    10.  
    11. Connect the positive terminal of the jumper leads to the positive battery post.
    12.  

  6.  
  7. If the fan failed to operated during testing, replace the fan.
  8.  

Cooling Fan Circuit And Fan

To test the cooling fan using the cooling fan circuit proceed as follows.

  1. Check the battery voltage at the battery and at the fuse panel. The battery voltage should be at least 12.3 volts. If less than 12.3 volts, charge or replace the battery. The voltage measured at the fuse panel should be within 0.3 volts of the measured battery voltage, if not check the wiring for a poor connection between the battery and the fuse panel, and/or the battery and ground.
  2.  
  3. Make sure the ignition switch and the climate control are in the OFF position.
  4.  
  5. Check all the fan fuses and replace any damaged or blown fuses with the correct amperage fuse as necessary.
  6.  
  7. Detach the electrical connector at the thermal fan switch located on the side of the radiator.
  8.  
  9. Using a suitable jumper wire, connect the jumper between the brown wire and the black/green wire of the thermal fan switch electrical connector.
  10.  
  11. The cooling fan should operate on low speed with the ignition switch in the ON position. If the cooling fan did not operate, detach the cooling fan electrical connector and using a voltmeter, attach the negative lead to the brown wire and simultaneously probe the blue and black/blue wires. If battery voltage is present, turn the ignition OFF and test the fan using fused jumper leads as described earlier in this section. If battery voltage is not present, check the circuit grounds, electrical connections, fuses and the fan relay.
  12.  
  13. To test the high speed operation of the cooling fan:
  14.  
  15. Using a suitable jumper wire, connect the jumper between the brown wire and the black/green wire and the brown wire and the black/gray of the thermal fan switch electrical connector.
  16.  


NOTE
This test requires the air conditioning system to be fully charged and operational.

  1. The cooling fan should operate on high speed with the engine running and the air conditioner switched on. If the cooling fan does not operate:
    1. Turn the ignition OFF .
    2.  
    3. Detach the cooling fan electrical connector.
    4.  
    5. Turn the ignition ON but do not start the engine.
    6.  
    7. Using a voltmeter, attach the negative lead to the brown wire and simultaneously probe the blue and black/blue wires. If battery voltage is present, turn the ignition OFF and test the fan using fused jumper leads as described earlier in this section. If battery voltage is not present, check the circuit grounds, electrical connections, fuses and the fan relay.
    8.  

  2.  


WARNING
Do not allow the engine to operate for a prolonged length of time without an operational cooling fan, otherwise, severe mechanical damage could occur.

 
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