jamesinger

So, I admit I am kind of a slow learner.

A few years ago, I got a B8 Avant with multizone auto A/C. I set it between 68 and 72 depending on the weather and would forget it unless I felt too cold or too hot. This worked the entire time I owned the car and I never gave it any thought.

Almost 2 years ago, I got my 997.1 C2S, which had a similar A/C system but single zone. I got the car, set it between 68 and 72 and forgot it...for a little while but then if it gets above 90, 68 doesn't feel like it is going to ever get there. Also, the fan seems to be roaring.

Last week, I was in my wife's Bolt and I had the same experience. I felt like setting the car at 68 didn't make it feel like it was ever going to hit 68 and the fan was blasting.

I mentioned it to her and she said, "I just set it on Lo and modulate the fan."
hmmm.
Then, when she did it, I noticed the air was coming out ice cold so I asked her if the air comes out colder in Lo than at say 68.
Yeah.
FML.
You learn something new every day.

I asked a friend who has a 997.2 GT3.
He sets it at Lo and modulates the fan.
He asked his HVAC friend because I brought it up and neither of us know that actual answer.
HVAC friend agrees with what I found through GOOGLE:
"Setting to the lowest temp and adjusting the fan makes the car air conditioning more efficient, will dry out the air less, and can actually save some fuel. Why's that? In a typical A/C system, the air is cooled to 38 degrees. If you set the temp higher, you are actually forcing the system to re-heat your air, which takes more effort, burning more fuel."
So, for the past 5 years, I have been cooling air to 38 to heat it back up to 68 to 72?

What is your July-September A/C ritual?
What about other months?
In CA, it is pretty much over 75 for 8 months of the year, so I use my A/C more than I do not.
Also, I never use heated air here unless I am with someone who wants to use it.

What do you guys think?

EDIT: I was just talking to my cousin who has a 718, and he also just sets it at Lo and modulates the fan. That is pretty much all the evidence I need. I guess I was living under some kind of false belief that the "auto" mode was real? I am still interested in what you guys do, especially people in TX and AZ...

Steph1

Interesting , as my A/C can be puzzling at times. Rather than warming the temperature after cooling it like your friend suggests, seems like my 997.1 stays as cold as it can be, but modulates the fan to blow higher or lower depending on the set temperature when on auto.

I can even confirm that when it has reached the desired temp, the A/C automatically shuts off and the fan blows cool but not ice cold until the temp goes up and then the A/C comes back on and cools the air again to meet the set temp.

Where it bugs me, is between the set temp and the re-start of A/C. It seems like it waits until the temp has gone up a few degrees before it comes back to life, and I can actually feel that the temp is higher than the set one before it cools the air again.

So, with this said, I like your suggestion and will try it this way and see if I prefer it like that.

jamesinger

my friend with an M3 said he leaves his a couple degrees lower for the exact reason you stated. Also, it seems more intuitive that the condenser would blow a certain temp, and the auto feature would modulate the fan but now I am thinking that this is not the case. Regardless, I have been wondering why the A/C is so inconsistent, and I think it is because if you set it at what I would consider a normal comfortable temp like 70 or so, depending on outside temp, it will heat or cool the air. Being in So. Cal, I never want heated air really, so I try to counteract the heat ever coming on. I guess the auto part was warming the air a bit though to keep the temp in my car at a certain rate that is still lower than ambient temp, so the A/C is on. ???

Bruce In Philly

It's a sports car. A/c sytem sucks. Get used to it.

Peace
Bruce in Philly

ADias

Curious... what do you mean by setting the AC to Lo?

jamesinger

just the lowest temp possible. When you keep sending the temp down, mine will read LO...or low.

jamesinger

lol. I was just having this same discussion but about the stereo yesterday. Friend's wife said the stereo in her super ancient Prius is better than the 997.2 GT3. I was like, "it has a stereo?"

I am almost inclined to start an "I HATE MY KEY FOB" thread but there are enough already. There are only a few things I do not like about my C2S. Right now, the list is:
#1 Key FOB
#2 The A/C.

ADias

So you say... manual mode, set temp very low (or at Lo), adjust fan volume. Yes, I agree that the AC works more efficiently with a low air flow over the evaporator.

jamesinger

That will be my new strategy.

It seems that the more people I talk to, the more people just do that with newer cars that have auto AC, especially in summer. It's 95f outside right now at 2:30pm pst. :-(
People can comment on how that is not really hot. I know. TX, AZ, the entire middle east... but anything that goes over about 85 is not where I want to be personally.
So far:
2019 Bolt
2018 M3 ZCP
2018 718 GTS
2010 GT3
and a few people on here,
owners have all said they basically do not use their auto climate control and just set the temp to low and modulate the fan.

ADias

It's fine what you do but I do not see the AC struggling in a 997.2S in 90F weather set in AC Auto and temp at 72F. So you may want to investigate what is going on with your AC condenser radiators up front - they may be plugged with dirt/leaves. Just a thought!

jamesinger

Thank you for the advice. I will vacuum everything out today for sure!

I didn't really think of it as an issue until it went over 100f and I noticed the temperature variance in my 2 current cars. One is only a couple months old. Before that, I had 3 other cars with auto climate, and with all of them, there is a moment in the year where the heat seems to render the auto feature useless. I mentioned it to my wife and that is when she told me that in the LO/lowest setting/LOW...whatever, the AC is pumping air out and you can modulate the fan accordingly like people's old school non-auto AC systems when it is set to cold. By setting mine at 68-72, it is essentially as if in older systems, you did not have the dial slammed to the lowest setting while running the AC but kept it at a bit warmer of a setting.

This has never been an issue for me from January to July but with my last few cars that have had auto climate situations, August (at about 100f every day), seem to not be able to handle the heat well. In any case, Friday, I drove for an hour down to Corona and back in 100f weather, using the lowest setting while modulating the fan, and I found that a lot of the time, the fan is between 1 bar and 5 max with the car as cool as one would want, whereas if I run the auto AC at 68 or so, the fan is just blasting full on but the air is coming out less cool.

It is kind of a stupid thread because IDK what I was expecting from "auto climate control." It is pretty much the same thing as old school climate controls with a digital interface, which brings me to the connected topic where I feel a lot of tech is just poorly working overly complicated versions of analog stuff that worked fine.

JustinCase

Interesting thread. I never put any thought into this subject at all -- I just set my A/C on Auto at 70 degrees F years ago, and adjust *neither* the temperature *nor* the fan. Now I understand all those threads about worn, illegible TEMP and FAN controls. Mine still look brand new twelve years after the car was manufactured. That said, it's a rare day in the Pacific Northwest when it's over 90 degrees F, and the dewpoint is always much lower than most of the country. I suppose I might be giving up some gas mileage, but I doubt it is consequential. Also, just vacuuming/blowing out the radiators from the front is rarely sufficient. It is always impressive to me how much more stuff comes out when blown out from the back!

jamesinger

Thanks for the tip!!

Yeah, this has only been an issue really above about 90, definitely above 95, and traffic here seems like it is getting worse, or something weird is going on the last month. I never had an issue with this kind of thing in the bay area or when I have stayed in your neck of the woods. I love it up there. I have friends and family up in Tacoma, Gardiner, Anacortes, and on Orcas Island. I hope to move up there some day before I melt.