carbonblackcab

I usually turn on the AC (and ventilated seats) a few minutes after I start the car. I turn the AC off when I am a few blocks from my destination. I turn up the fan when i turn off the AC to make sure I dont have condensation in then vents (to prevent the moldy smell).

I wish porsche had the feature that Mercedes has where can keep the air circulating for a few minutes after you stop the car. I really miss that feature from my CLK 430.

Macster

I too shut off the A/C compressor a distance from my destination to give the A/C system hardware/vents time to dry to lessen the chance mold/fungus can take root. Once they do they are very hard to eliminate.

As for the A/C compressor being on when the engine is started I believe the A/C compressor is not engaged or its variable stroke setting is at zero compression so the A/C compressor presents very little additional load to the starter at engine start.

But it doesn't hurt to be safe and making sure the A/C is off before starting the engine is ok. I do it too.

Sincerely,

Macster.

DLennox

It's kind of a waste with the windows down and the sunroof open!

dansen

I always have it on Auto. When I started the engine, the unit was completely off. Couple seconds later, the computer will decide to turn on AC or heater to get to the temp that I set. I been doing this to all of my cars that have auto climate control for over 20 years. oh, I do turned it off when I have the top down. I thought this is in the manual. I do see other turned it on and off everyday and had problem with their switch.

Fisher

I concur 100%. Never turn the A/C off, even with the windows down and sunroof open. Use the sunroof every day, usually just to hear the exhaust. Works great here in SoCal and no moldy smell in my 997.1 GT3. I believe it's the same A/C as other 997s. BTW I don't claim to understand how the A/C condenser can be turned on or off to control the moisture in the vents. I just tend to not fix things if they aren't broken.

Can't say the same for the wife's SL55 AMG, which sometimes has the moldy smell at start-up. The Merc dealership recommended using a mold killing spray in the ductwork. Guess I'm not using the proper technique, but it's not bad enough for much concern.

pilfjd

Car is garaged so I'll leave AC off and drive around with the windows down. Auto goes on when the car has been sitting and baking in the sun, when wifey is in the car, or when I'm wearing a suit.

JCH

i think it is possible to turn AC off fully.

Turn the fan speed all the way down. Touch the fan adjustment to go down again. "Off" appears in the display on my system and I am pretty sure it is fully off.