Nissan Repair: ventilation, controller area network, three knobs

Question
I used to be able to recirculate air when vent was in a floor or floor/vent possition (in air, a/c or heat modes).now when i move dial to floor a/c turnes on, I have to manualy turned it off and recirculation is not working. Nissan things that it is a working properly.In floor/vent possition recirculation is working good. I think reirculation suppos to work in any possition except defrost and defrost/vent. I have 2006 Altima 2.5L with no climate control(all manual).21,000 miles.
thanks Serge.

Answer
Serge,

The dealership should hook your vehicle up to the Consult III Scantool and look at the controller area network and see what the computer is commanding the blend doors to do.  You just have three knobs?  If this is correct a computer still drives the actuators.  Another option is to get into another Altima and see what it is doing.  The AC should not come on with the floor vent.  The blend door for recirculate and outside air will do what you say...  Mine does this...