No air from defrost vent - not opening

[Tourenwagen]

Hopefully there is a quick answer to this one. Got a 2/92 525i 5-speed that doesn't blow any air from the defrost vent onto the windshield. The blower motor runs normally throughout the speed range. The vent slide control feels normal, and air is controlled properly at the dash. I don't remember whether the footwell vents worked either, will have to check again.

Is this caused by the servo that controls the flap, or the slide control on the dash panel? Or is it more in depth than that?

[calmloki]

WooHoo! Post 100 and it may actually be of use! When I pulled apart the dash and front of the heater box on my '93 525iT the dash vent temp was controlled by a servo motor on the Right side. The heater and defroster flaps are directly controlled by the levers and cables. I would check the back side of the slide controls - on mine one of the cable end clips was out of it's socket on the controller, thus not properly operating, as the outside of the Bowden cable moved with the inner cable.
Hope this helps, Tom Walrod

[athflying79]

I would take the side panel under your glove box off and pop out your A/C controls. That way you can see both end of the the Bowden cables. My defrost vents aren't working, but the cable is fine. My flap is stuck inside somehow. I can not move the lever back and forth. It will move some, but if I use to much force, it feels like something is going to snap. Good luck!!

[David Barber]

Hopefully there is a quick answer to this one. Got a 2/92 525i 5-speed that doesn't blow any air from the defrost vent onto the windshield. The blower motor runs normally throughout the speed range. The vent slide control feels normal, and air is controlled properly at the dash. I don't remember whether the footwell vents worked either, will have to check again.

Is this caused by the servo that controls the flap, or the slide control on the dash panel? Or is it more in depth than that?
Barry,
curious what you found! I just purchased a 92 525 wagon and the vent slide valve for the defrost had been forced so that it separated from the gear in the control, got that fixed but it appears to be the flap in the heater(air distribution) box itself, first thought was that something was lodged in the box since I had pulled a couple pencils and a warped bic pen from the defrost vents, went through the side of the heater box with a uni-bit and created a 7/8" hole under the flap and poked,probed,etc. nothing. The Bentley is useless, bad pics etc. ETK and TIS pretty much useless as far as diagrams. At this point I have concluded that the flap is being held from operating fully by a bad acuator/servo/stepper motor. On my E28,E30 if you wanted defrost you just slid the levers to the right place. This is a BEHR IHKR lll, ?'s Does the car have to be up to temperature and running for this to operate fully? Does the whole heater distribution box need to come out to replace the actuators? Any help appreciated, pics or links.
Thanks,
David

[David Barber]

Barry,
curious what you found! I just purchased a 92 525 wagon and the vent slide valve for the defrost had been forced so that it separated from the gear in the control, got that fixed but it appears to be the flap in the heater(air distribution) box itself, first thought was that something was lodged in the box since I had pulled a couple pencils and a warped bic pen from the defrost vents, went through the side of the heater box with a uni-bit and created a 7/8" hole under the flap and poked,probed,etc. nothing. The Bentley is useless, bad pics etc. ETK and TIS pretty much useless as far as diagrams. At this point I have concluded that the flap is being held from operating fully by a bad acuator/servo/stepper motor. On my E28,E30 if you wanted defrost you just slid the levers to the right place. This is a BEHR IHKR lll, ?'s Does the car have to be up to temperature and running for this to operate fully? Does the whole heater distribution box need to come out to replace the actuators? Any help appreciated, pics or links. Does anyone have a method for testing the acuators? If the car is off shouldn't the lever operate fully left(closed) and to the right(open)? What happened to simple? Bowden cables are fine.

Thanks,
David

[Gledhill]

I have the same problem with my 1990. Before I tackle the job of pulling my dash apart can someone tell me how to get into the back. One person suggested the panel beside the glove box. Are there any other things that I need to consider before doing this?

[Gledhill]

I pulled everything apart. The cables behind the controls are connected properly but when I followed the cable for teh defrost it went to nothing. It looks like something might have been broken off the "vent controller"? Does anyone know if this can be fixed or where I can purchase the vent controller?

[David Barber]

I pulled everything apart. The cables behind the controls are connected properly but when I followed the cable for teh defrost it went to nothing. It looks like something might have been broken off the "vent controller"? Does anyone know if this can be fixed or where I can purchase the vent controller? The end of the bowden cable for the defrost flap is in on the passengers side of the HVAC box and if I remember right its the red one, the lever is in a verticle arrangement, there should be an eyelet bent from the cable that slips over the lever. If the flap lever is there you can manually move it front and back, if it is broke it should be obvious, the only way to replace the flap would be to completely remove the heater, ac and find a flap from a donor box, I have an obstuction down in mine and am only able to move the defrost lever half way and am going to save the heater removal till spring.
Good Luck!
David