Thanks for making this post as I've been troubled by the same question on my 560SEL.
From playing around in my car, it seems that the rear vent in the console will do cooled air with the A/C on during the summer. Is this correct? Also, where are the ducts for the heat? I haven't seen anything under the seats yet and the duct work under the front carpets seems to run back into the console, not under the seats.
'87 560SEL 267K (177K on motor) Blue/Blue
'98 Buick LeSebre 60K (wife's car)
'56 Imperial Sedan 124K
'67 Dodge Monaco 130K (Sold)
'87 Chrysler 5th Ave 245K and going strong (sold)
'73 Plymouth Satillite 175K (sold)
'96 Chrysler LHS 80K (totaled)