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Date: Thu, 30 Jul 1998 20:09:17 -0400
From: "Brant M. Miller" <>
Subject: <E34> Microfilter

Peter, the Bentley Manual and other sources say the microfilter started in 1992, so you should have one.

Re instructions for changing same, there has been much on the Digest over the years and the Bentley Manual can also help. I've reproduced my hash of good advice originally provided by Kurt Gibble and Dan Quicker below - my appologies to the two of them for any deteriorations I may have introduced. Kurt had (has??) the instructions on a web site, however, I've lost the URL.

When you are all done, you will have a new appreciation for how footprints get onto BMW headliners!

Kurt Gibble (9/91 E34 M50 5sp) provided most of the below information with comments by Dan Quicker ('95 540ia) incorporated. I've added a bit to reflect my experience with the microfilter on my 1995 525i.

Working somewhat from Chilton (just short of useless for this job) and mostly from BMW fiche:

  1. Remove glove box by removing the retainers holding the strap and gas strut (if present) from the sides of the glove box. Lying on the floor, loosen and release the latches for the rear hinges. Dan says "Glove box is now sitting on your head." Just reach under the glove box and pull the snap connector releases down. The connectors will then slip off the mounting rod.
  2. Remove the carpeted panel on left side of pass. footwell. On Dan's 540, the carpeted panel was screwed to a gray mount that is removed by pinching the mount and sliding it out. This mount would have been in the way when you slide the filter out in step 6.
  3. Remove the black cover on left side of glove box. (On this, the fiche has the wrong picture in Sec. 64-31/2 but I believe Fig. 2 of Sec. 64-31/1 is correct.) Remove the small duct going to the RHS of pass. footwell. On the 540, the black cover and the RHS footwell duct should be removed as one piece. On the '95 540 there are 4 screws and this sounds like what I remember for my '92:

a)1 holds the top of the black cover to the dash.

     b)2 secure the duct behind the glove box hinge mounting bracket. On the
     '92, these easily fall down in between the bracket parts - it's hard to
     retrieve them from there!

     c) 1 well hidden screw holds the duct directly above the 90 degree bend it
     makes from the console to the footwell. It is on the top side of the
     duct. (On my 95, the fourth screw connects the pannel to the top of the
     glove box compartment.)

Turn the assembly out of the way. (The wires to the flashlight don't have to be removed.)

4) On the '92 (and my 95 525i), remove the wires for the HVAC control unit (I believe that's what it is) at very front & bottom of the console, right next to the fire wall. Wires have a v nice, arguably over-engineered, connector - lift the lever up and the plug automatically comes out. On my 95, the lever does NOT lift up!! Reach behind the lever and press the catch in. Then rotate the lever back. A cam will disconnect the electrical connector.

Release the clip and pull out the control unit. Dan says that on the '95 540, you can leave the wires attached and just set the unit aside - pick your poison.

NOTE: Over the AC coil and heater core, there is a black cover with 7 T15 screws. The microfilter's not under there! You don't have to remove it - beender dunyat (see step 3 about wrong fiche picture.)

5) Down further & recessed (toward the center line of the car) is a small funny shaped (tall and thin) white cover (on mine) with 1 or 2 screws (T15 I believe). The microfilter is under there. I think you get it loose and then have to rotate a lever to get it out.

On the '95 540 (and on my 1995 525i), Dan says the white cover is right next to the control unit. It is
held with 1 T15 screw and a cam lock lever at the top. Loosen the screw, Turn the camlock counterclockwise. Remove the White cover. The filter is right behind it. As you can imagine, the white cover is as tall as the filter (5"?) and about 1 1/2" wide.

6) Pull the filter out. While your there, clean out any junk in there that you don't want to blow out of the center vent and into your face. (Leave the junk that you do want blown into your face.) (Be careful not to damage the air conditioning radiator while cleaning the coils. It is easy to mash the fins.

7) Trivial Step: Assembly is reverse.

Took me ~2 hours first time because of the brevity of Chilton and the error in BMW fiche. Should be a 30-45 min job 2nd time. (Took me about 4 hours first time. Much of which was spent on the electrical connectors.)

From: Peter B <>
Subject: <E34> 1992 525i, Microfilter question

The car in question is a manual 1992 E34 525i with the M50 engine. (7/91 production date).

Does anyone know if this car has a microfilter like the E36's that needs to be replaced periodically? The A/C intensity has dropped off somewhat (though he it never really was that strong to begin with) and I was thinking maybe the problem is with a dirty microfilter if there is one? If there is one is it as easy to replace as on the E36's? Thanks. <

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