W140 320SE Airconditioning
 

My air conditioning cools at 7 deg through the centre vents. Could anyone comment wether it is normal for the outside vents to have as much as 12 deg difference to the centre vent temperature? Surley it can't pick up that much heat through the ducting.

I never seem to receive much cooling from the center vents unless I push the the blue button between the vents.

Centre vents are fine but left and right outer vents are my problem.