I have the same 2 symptoms on my 95 C280!
Recirculation flaps stay open at all times.... letting air into the car from the side and defrost vents, more air the faster I drive.
Also, when I have the AC on, the center vents close when I accelerate!
I also hear a slight humm sound of some sort when the climate control is OFF, and this sound goes away when I turn the CC on.
I am able to retrieve codes via the CC unit, luckily.
The codes I keep getting are:
60: A/C Compressor, Electromagnetic Clutch (A9K1), CAUSE: Short Circuit. Intermittent.
82. Switchover Valve Block (Y11/3), Tempering Flap, CAUSE: Short or Open Circuit. Intermittent.
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)