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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 11-13-2015, 10:10 PM
wolfnick wolfnick is offline
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Mein Auto: 320I
HVAC - no / very little cabin airflow

Hi - been searching threads in relation to a long standing issue I'd been having, as well a multiple mechanics having looked to find the cause over the last couple of years. No joy until today! There are several threads around re this issue and I hope this may at least point people in the direction I've found to solve my issue (almost) as to date I hadn't found anything online or by paying mechanics to give me a host of possible causes but no solution

- 1997 E36 320I - right hand drive
- electronic HVAC control system

Symptoms:
Little air flow into cabin (I mean hardly a thing unless you touch the vent to feel a wisp of air coming through any of the vents when on max fan speed!!)
Fan works fine - comes on when requested, goes off when requested. Can hear the fan speed increase and decrease as instructed on control panel
Cabin Air Filter replaced and cleaned the area out (as suggested in many threads to solve air flow issues)
FSU replaced as implied on many threads to be the cause

Solution for me:

Under the bonnet, the air intake box in the centre directly below the windscreen. I removed the plastic ''mesh'' clip cover and on the passenger side (for RHD) , reached inside and towards the front I could feel a flat roundish shaped item that easily moved from left to right and back again. On moving this, you can just about see the inlet flap at the back move in and out. Moved it by hand and WOW - its like sitting in the car with a hair dryer on full blast now!

So I either need to now dismantle to gain access (or have my fav mechanic do it) as I presume there is a cable, actuator? (not sure) that has broken and was stopping this from allowing the vent to open. Sorry I don't have the final solution, but when I get the car in the garage in the next few weeks I'll post an update if needed.

Cheers
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  #2  
Old 11-14-2015, 04:50 AM
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drivinfaster drivinfaster is offline
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i believe the system has a bunch of little servos that control the blend doors to restrict or allow airflow. sounds like one of them may be kaput.




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Old 11-14-2015, 08:43 AM
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ZeGerman ZeGerman is online now
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The flaps are typically vacuum actuated, no? I think some of them are, but I don't know if they are all like that, or if others use electric servos.

Anyhow, thanks for posting this. I'm sure others will find this information useful in the future.
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Old 11-14-2015, 02:30 PM
wolfnick wolfnick is offline
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Cheers for replies. It all helps greatly
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Old 11-15-2015, 06:25 AM
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drivinfaster drivinfaster is offline
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Quote:
Originally Posted by ZeGerman View Post
The flaps are typically vacuum actuated, no? I think some of them are, but I don't know if they are all like that, or if others use electric servos.

Anyhow, thanks for posting this. I'm sure others will find this information useful in the future.
a lot of vehicles do use vacuum to actuate the blend doors and direct the airflow, but it seems that more and more vehicles, especially with automatic climate controls, use little motors to control the temperature as well as direction of airflow.

when i pulled apart my 328i there were no vacuum lines to the hvac box that i can recall.

lots of wires and servos, though,....





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Old 11-15-2015, 07:33 AM
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ZeGerman ZeGerman is online now
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That's actually good to hear. I'd rather have wires and servos than vacuum lines, I think...
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