Norway S8

I recently changed the blower motor on my 2002 s8 D2 after it died on me, but then i got a new problem and thats no air flow through any of the vents, well i get air when i set it to defrost.
But if i run a diagnostic test then i get full air flow, i asked the local Audi service station and they told me it had to be a problem with the control unit, so i found 1 on ebay and changed it but stil have the same problem with no air flow.
Is there anything else that might prevent the main flap to open? like a sensor maybe?

jfrahm

Some people got new HVAC blowers which were wired reverse of the old ones, had to rewire to reverse polarity.
*edit* it sounds like you get airflow sometimes when in defrost for example but otherwise is the fan quiet or roaring? Fan sounds like it's blowing air but no airflow?

NOLAessate

Same situation with my 02 S8 as Jfrahm. Lots of blower noise but very little air. Blower motor was reverse wired. I had changed the control unit also. Had the blower rewired and system functions as it should.

Norway S8

yes the blower is running but no air flow, but if it was reversed wiered then it's wierd that i get air flow during diagnostic test run.
but il check this weekend to see if it is reversed.

jfrahm

A miswired motor does not make sense if it blows normally in diagnostic tests, but maybe if it sorta blows sorta normally (like you feel air moving) maybe that's the issue.

Otherwise run through all the sensors, see if the output makes sense. Check to see if asking for full heat or max cold works. In VCDS you can probably list all the flaps and flap angles and compare those readouts to when you are not getting air to when you are (in diag tests).

Norway S8

Well i did test the miswiered motor tips you guys gave me and now it all works like a charm, so i got no idea why i was told it worked during diag test.
anyway thanks alot for the help guys

Number48

My apologies for hijacking an old thread. My A8L is a fairly newer car to me and I haven't cared about this until now. The a/c fan runs and blows normal at lower speeds, but there really isn't much difference in airflow between half-speed and full speed. You can hear the motor working harder but don't get more airflow. Going through the mode selectors, the positions change from defrost-vent-floor. I don't know if any work was done on this system before I got it. The previous owner mentioned the Audi tech said some flapper door deep below the fan is to blame. I do get the clicking in the dash while driving, like sometimes it wants to correct something to maintain temperature, but cant. Thoughts before I pull the motor and start blindly digging around?

jfrahm

Check the filters? If they are clogged up that'd limit airflow. Underside of the hood.

audinutt

Check the wires for the blower motor, if you can see the connector you'll see what I mean, if the motor was changed it is highly likely the polarities are reversed.
This caused me to heavily discount my wife's d2 when I sold it to a friend, then I discovered the problem when I changed my s8's blower.. same issue, little airflow after changing the blower.
I looked at the wiring and discovered they wired them backwards from the manufacturer. (these were genuine audi parts too)
https://forums.quattroworld.com/a8/msgs/101608.phtml