axhoaxho

In old days, like in the 80's...

... I was taught that it is a good habbit to to turn-off A/C before I shut-down the engine (something to clear the pressure in the lines?)

... Also, to make sure the A/C is OFF before I start the engine (especially in cold winter morning, prevent extra load on engine start-up?)

... Plus, don't turn the A/C ON or OFF on freeway (something about huring the A/C clutch to engage in high rpm?)

Now with modern cars like our 997, do the above still apply? If not, does Porsche implement some new technologies to making sure that the old day habbits are not necessary in the new cars?

Thanks, and with best regards,
- Alex.

PAULSPEED

Hi,
With temperature control settings, I do not think
the old rules still apply.
Paul

wilfred

1&2) As a habit, I always turn off the AC before engine shut-down because the AC does take a lot of juice out of a battery that's not being charged by the alternator. So if your battery is getting old/weak, you may not be able to start. But I do not think it's harmful in anyway if you do leave it on. And as long as your battery is in good health, nothing to worry because as soon as your engine turns over, the alternator will charge up the battery.

3) never heard of this one

waiting for PDK

Alex,

A reason for shutting off the AC before turning off the car is to allow the ductwork to warm up closer to ambient humidity while there is still airflow. Simply turning off your car can allow condensation, and possibly mold, to form in the ductwork. I don't know how common this is but I have a friend who had it happen in his Jeep--it really smelled and cost a bundle to get fixed.

cdodkin

I''l 2nd that point

Always run the fans with no AC for the last mile before parking the car - that way you will avoid condensation in the AC system, and those moldy car smells later on that are so hard to remove.

ChipAZ

I always have the heat and AC off unless I am actually using it. I always use the encon. mode, why run the AC in the winter unless your trying to defrost the windows? I don't know why Porsche has it where you have to select the encon. mode everytime you play around with the heater?

Alan Smithee

Old habits are hard to kick, and I still wait until the car is at normal temp before turning on the AC (or taking it over 3,000 RPM). But I rarely use AC anyway.

I got into the habit of turning it off 5-10 minutes before shutting the car down due to the aforementioned mold issue. It was chronic in my E46 M3, and occasional in my B6 S4...depends on the car's HVAC design...not sure if it is a potential problem with the 997.

I've never heard of #3 either...but cars these days aren't turning very high RPMs at freeway speeds anyway.

axhoaxho

Thanks folks,

I guess I would keep my old habbits afterall

For #3, I learned it from the Rennlist 951 board (yes, I also have a 951 and a 986S). One time my A/C fuse kept blowing off, I replaced the fuse with a new one, and as soon as I turn on the A/C the new fuse is blown again.

I brought my car to the shop. It found out that the A/C compressor clutch was the problem. After replacing the A/C clutch, no more blown fuse.

I then asked the Rennlist 951 board. Some folks suggested that to prevent stress to the A/C compressor clutch, it is a good habbit to prevent turning On or Off the A/C during freeway.... Something about engaging the A/C compressor clutch in high rpm (I guess the A/C belt is rpm dependent?).

I didn't understand the technical details, but since then I have the habbit to not turn On or Off A/C on freeway...

Thanks again, folks.

With best regards,
- Alex.

Pete Lech

My AC comes on automatically whenever I start the car. It stops when I turn the car off. I have never had a mold problem in any of my Porsches or other cars.

Perhaps in Louisiana or other very humid areas, it could be a problem, especially if you have a clogged evaporator drain hose. A little mild bleach solution sprayed into the intake while the fan is running should fix things up.

vitman

25 years of driving in Florida and almost never shutting the A/C off. Many cars..Toyotas, Jeeps, BMW's, a 2001 BoxsterS for 4 years and now a 2006 997S for over a year. I've never had any A/C issues and no mold, smell, etc. You're wasting your time worrying about this issue. (By the way Toyota A/C is the best but I'll still keep my 997S) Just leave the A/C on.

Alan Smithee

Perhaps with the 997, but it is definitely a problem in some cars. BMW issued a TSB on the E46 3-series because of it.

Sniff

Reviving an old thread. I have a 2006 C4S, and the air conditioning and fan (set to med-high) always come on right at engine start-up. This happens regardless of what the climate control system was set to when I shut the car down (I usually turn everything off on the climate control panel before removing the key from the ignition).

Is this a Porsche standard setting I just have to live with? Better yet, is this something I can change? I read through the owner's manual and it doesn't specifically mention this. I find it somewhat annoying the car is doing something I haven't selected nor do I even want. My early morning drives so far have not required a/c. Thanks.

Sean

Luckymba

I have a 2005 and mine only comes on when I turn it on and always stays set at what it was on last. I've never heard of this before.

spudster

Sounds like you have the climate control memory activated. In my PCM manual it says, "If climate control memory has been activated, your personal settings for the air conditioning will be restored whenever the vehicle is started with your key." It can be deactivated by pressing the set button and selecting individual memory. Uncheck the climate box.

Sniff

Thanks for the info Spudster. Is that info in the PCM manual or the owners manual? I read the section of the owners manual covering automatic air conditioning and it didn't mention anything about climate control memory.

Sean