BMW 318/325/M3/525/535/M5 1989-1993 Repair Information

Microfilter

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BMW uses a microfilter to clean the air being passed to the passenger compartment. The unit cleans pollen, dust and other particles from the air to allow better driving comfort. A reduced flow of air from the vents is an indication of a clogged microfilter.

REMOVAL & INSTALLATION



E30 3 Series
  1. Open the glove compartment door and remove the inside trim at the heater side.
  2.  
  3. Remove the glove compartment door straps and the hinge mounting nuts. Remove the door.
  4.  
  5. Remove the 4 screws holding the cover on the side of the heater unit. Remove the microfilter from under this cover.
  6.  
  7. Install the filter, cover and glove compartment door.
  8.  

E36 3 Series

Canadian versions not equipped with air conditioning use microfilters attached to the blower housing. These filters are removed by accessing the blower housing through the engine compartment. The other vehicles have the microfilter in the heater and air conditioning unit within the vehicle. This procedure covers the internal microfilter removal and installation.

  1. Place the vents above the glove compartment straight forward and remove from the dashboard.
  2.  
  3. Remove the 6 screws holding the glove compartment and remove the unit complete with the lower trim panel.
  4.  
  5. Remove the footwell duct for the heater. Remove the screws holding the control unit bracket and tilt down.
  6.  
  7. Turn the lock and remove the cover. Pull the filter out of the housing.\
  8.  

To install:
  1. Install the new filter and replace the cover. Turn the cover lock.
  2.  
  3. Install the control unit holder and the heater duct.
  4.  
  5. Install the glove compartment, trim and the vents.
  6.  

E34 5 Series
  1. Remove the glove compartment and pull the trim panel out from the rear clip.
  2.  
  3. Remove the cover by disconnecting the clip and pulling out. Remove the air duct screws and lift out.
  4.  
  5. Disconnect the wires from the control unit. Remove the stage from the filter cover.
  6.  
  7. Remove the cover screw and turn the holder. Remove the cover and the filter.
  8.  

To install:
  1. Install the filter, cover and stage. Connect the control unit.
  2.  
  3. Install the air duct and the cover. Install the trim panel and the glove compartment.
  4.  

 
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