Minimizing A/C use
 

I have had a rental car for the last two days. 2010 Chevy Malibu.

At first, I hated the idea of driving this car. Compared to our 2008 Jetta, I just knew that this car was going to be crap.

However, I am now eating my words.

I am almost completely sold on this car for the simple fact that the A/C system is incredible.

As an efficiency guru, I do my best to minimize A/C usage whenever possible. I do this by recirculating the air in the cabin and toggling the cooling function.

Unfortunately, the Jetta's A/C is kind of crappy to begin with. Secondly, it seems as though the air maintains its coolness for only a short time before it's warm again (with A/C off and circulate on). This frustrates me to no end. It's almost as if the car is poorly sealed or something.

I drove the malibu yesterday for about 30 minutes. With the air circulation on, I turned the A/C on for all of about 2 minutes when I first started driving. THE AIR REMAINED COOL FOR THE REMAINDER OF MY DRIVE.

I guess I'd also attribute a bit of this to the fact that the dash board of the malibu is white/beige and the jetta is dark grey/black.

I am so pissed at my Jetta. So utterly disappointed, especially considering that the car's gaskets aren't even old, it's a 2008.

Please give me some thoughts...

On an unrelated note, the malibu was also superior in that it is equipped with instant mpg readout on the instrument cluster. I found that the mpgs of the malibu were quite similar to that of the Jetta as well.

oh, I forgot to add...

The jetta is dark grey, while the malibu is bright white. I'm sure this makes some kind of difference as well.

There might be other explanations. Generally, the newer the vehicle, the tighter the weatherstrip seals are.

Simple: Trade your Jetta in for a new Chevy Malibu. Then you'll be happier.

Even just after a couple of years?

Ohh, now that's another story. But a Chevy can last a long time - especially if you are lucky and don't drive it much...:cool:

Living as you do in Florida and driving a grey with a black / grey dash car in the N. American Summer with an air conditioner designed for European Summers it is hardly surprising the thing is struggling.

Isn't is obvious?

Newer car with lighter colours and designed for the conditions you are driving it in.

Peter.

So is it more fuel efficient to turn on the AC full blast to cool the car then turn it off and then back on when it's hot again or to just leave it one a lower setting to keep the car at a constant cool?

All depends on the system design. My Jeep's AC system has a pressure switch that turns the compressor on/off as needed. Some old AC systems keep the compressor on all the time the AC is on and have a recirc valve that bleeds excess pressure to the inlet side of the compressor to keep the pressure constant.

What I do is when I start driving I blast the AC with the Fan on 4, until the temp is where I want it, then I slow the fan down to 2, and adjust the hot/cold dial to where it keeps the temp constant.

That's interesting.

Also, some fan speed controllers are setup so that they draw the same current regardless of setting. My Jeep draws more current at higher settings than lower. You can test this by checking the battery voltage at different fan speeds while the engine is off. If it always draws the same amount of current, the voltage will be the same regardless of the fan speed. If the current draw varies with fan speed (higher speed, higher current draw) then the battery voltage will be lower at higher fan speeds. If you have the engine on while doing this the readings will be inaccurate due to the alternator charging the battery.

Just to be clear, I NEVER use my A/C's highest setting. What I meant by toggling on and off, while maintaining air circulation, is that I press the A/C button. This is the button with the "snowflake" on it. In other words, I'm likely to leave the setting on "2" throughout my drive. Also, I'm likely to use the "recirculate" setting throughout as well. This is technically not using the air conditioner, unless you've pushed the respective button.

The concept is basically the same as any other method of conservation. By limiting your use of the air conditioner, you are actively conserving fuel.

I hope this helps you understand what I'm talking about. I'm certainly more confused now.

My rule of thumb is to use it as needed to remain comfortable. Hotter temps can cause physiological stress that can effect your driving and your perception as well as your reaction times. I'm much more alert when I'm cool, and get drowsy when it's warmer in the car. I'll take the penalty to remain comfortable and safe.

Couldn't agree with you more. It's becoming increasingly important to me to remain cool while driving in the hotter summer months.

My original point was that in the Chevrolet Malibu, I was able to remain cool without even using the A/C for 9/10s of the time.

Remaining cool while not running the A/C in most cars seems impossible. Desirable, but impossible. The malibu's cooling system combined the best aspects of these worlds. I'm able to cool the cabin to a comfortable level, shut the a/c down and still feel cool for the remainder of my trip.

This is what I'm saying: I'M IN AWE. THIS IS A HYPERMILER/ECOMODDER'S WET DREAM, so to speak.

on my upcoming roadtrip I'll be letting my girlfriend control the AC (YRMV, depending on your significant other) becuase her comfort range in the car is smaller than mine. she complains of it being to cold before I do, as well as complains of the heat before me. Ultimately it will average out fairly well, it won't get as cold, but also won't get as warm before she adjusts it.

Easy and cheap mods would be covering the dash with something insulating and reflective. A couple hundred would buy you good, metalized, heat-rejecting tint. It might be fairly easy to insulate your ducting into the cabin (be careful of the airbags!). More pricey would be to repaint part or all of the car with at least a brighter paint but perhaps even some of that new ($$$) heat rejecting paint (not available in a good black yet). Sheepskin seat covers are serving me pretty well too.

Great call on the dash covers. I've been wanting to get one for both of my cars for some time. My beetle's dash is gigantic and, of course, black.

dieselbeetle -

Yeah, I have a black dash cover for my dark brown dash. I don't think you want a reflective dash cover. You still need a dark color, otherwise the color of the dash will reflect onto the window. At least that's what happens to me.

CarloSW2

Joenavy85 -

Same with my wife. I have heard that the majority of women have a narrow temperature tolerance as compared to men. The following doesn't confirm what I am saying other than men and women's perception of comfort temperature is *different* :

Thermal comfort - Wikipedia, the free encyclopedia
CarloSW2

...amen--beware the woman in menopause!

i use my a/c no matter what it cost me and don't care i still avg 26-29 mpg in the city with them on and i have heart problems since birth and can't withstand heat...and yeah age of 31 kinda sucks huh i gotta live long in comfortable life!

man I'm learning so much

Impossible. I hate to burst your bubble, but someone has to. A sealed car in Orlando in July will soar to 150 degrees in 30 minutes without AC. It's simple physics. If you don't believe me, just park that Malibu, and sit in it, engine off, for 5 minutes, and see how well your imaginary insulation keeps the car cool.

Your rental Malibu must have automatic climate control. That's even worse than AC, since it's blending cool AC air with heater air to maintain cabin temperature.

^^^also to balance humidity

...exactly, because water vapor (humidity) "holds" heat. That's *why* a clear night will typically be colder than a humid night...water vapor can hold a lot of BTU's!

I have wondered about this too. I'm starting on a dash cover as a mod for cooling. I need an insulator to cool the vent-ducting just under the dash. I have an old wind screen heat shield I thought I could cut and tailor--maybe. But if I cover it with a dark color I will recreate some of the heat gain inside the cabin. I certainly can't use white or silver (!), but anything is better than my stock black! Any suggestions?

@Sentra-SE-R: I am sure you are correct that cars heat up in the sun, but car-off and car running with fan running after running the A/C are really different scenarios. The A/C unit will still be cooling recirculating air for a while. BTW, my tint keeps my car far cooler than you would expect: metalized, heat rejecting, and DARK, I don't get into a cool car, but it's a lot cooler. I'm working on the roof liners after the dash. I'm gonna be cool without A/C one day.

No automobile can avoid getting hot enough to fry an egg on its hood in Orlando Summer sun. All a fan does is move that 100+ degree air around inside the Malibu. So, park that Malibu in the Summer Orlando sun for half an hour, starting with it being 75 degrees inside. Take a house fan and extension cord with you. Do you seriously think it's not going to rise to 150 degrees inside that car within half an hour?

oh yes. I'm quite familiar with the reflection syndrome. However, on a recent road trip I had success with laying a towel over my dash. The towel was light blue and yes, reflective. However, the only times that this reflectivity gave me a problem was when the towel got bunched up. This caused distorted shadows and made seeing out harder (as you were saying). In other words, you get used to the reflective effect the light dash cover has, because it has no shadows or patterns that can become visual obstacles. THESE are what impairs vision, not the light color's reflectivity.

I never said anything about the car being turned off.

That's why, after a couple minutes, you turn the A/C back on. Then toggle off. Then on. Low fan. Internal recirculation. Takes away heat and humidity, runs the A/C a fraction of the time. Saves fuel. Nobody freezes. :thumbup:

Oh! Apparently one trim level of the 2010 Malibu (the highest level it seems) does have "climate control" instead of just AC: 2010 Chevrolet Malibu LTZ Sedan 2.4L 4-cyl. 6-speed Automatic Features and Specs

Beaded seat covers help. And I have found that opening the windows a bit 1"-1 1/2" on all four, actually helps the aero at speeds up to say ~50mph. So, I have not replaced the A/C fuse in my xA since last year; and I don't think I have used more than a day or two in the last three years. A little sweat won't kill ya'! Drink cold water or lemonade.

A white roof helps a lot -- this should become an ecomod!

I hate climate control. :mad: Moon Unit has it and when I select "Vent" sometimes I'll detect the a/c clutch engaging. :mad: So now what I do is select outside temp, get the reading, then match that for my interior temp setting- so when I put it on "Vent" I get "Vent". I'm thinking of installing an a/c clutch cut-out switch anyway, just to be sure.

Amen, though there are places where "a little" just is not the quota this time of year.

Totally true! But maybe not just white. There is all kinds of new crazy paint out there: Planet Supra Nano Heat Reflective Paint products, buy Planet Supra Nano Heat Reflective Paint products from alibaba.com

So you seriously think your rental Malibu's AC produced enough cold air in 2 minutes to keep the cabin cold for the next 30? In Orlando, in the middle of July? The laws of thermodynamics don't apply any longer?

You're not going to man up to the fact that the Malibu had to have automatic climate control, and you didn't notice it?

That's gotta be it. So in other words, the A/C IS on even when it's off!!!

If this isn't exactly so, can you help me to understand what climate control means?

I have 03 Malibu, 95 degrees out today, ac on/recirc on for first 15 miles temp OK. Turn ac off, recirc on, no change in temperature inside car for 15 minutes, turn recirc off, humidity & temp rises in minutes. I think the recirute button overrides the ac switch, it was without adoubt running, no change switching ac button on or off, all highway so I couldn't feel it cycling but I know it was. I'll try with the 10 Impala I bet it works the same.

Here's a great link to some wonderful information about climate control and similar systems and related woes.

Automotive climate control: Information from Answers.com

...'Mother Nature' has a nasty habit of not stopping the afternoon air temperature at balmy 72ºF but rather always seems to continue UP to 105-110ºF around here (southern California, Arizona, New Mexico, and Texas).

Couldn't agree more. I was in West Texas during the month of June. It got up to 113 during this time. Where A/C is concerned, this was an ecomodder/hypermiler's worst nightmare.

I guess in a car with a larger engine it is more subtle, but in my 1.9l tdi, the draw from the A/C is quite significant.

Yes, Neil. This should definitely be added to the list. Believe me when I say that ALL of my future vehicles will be white.

Unrelated question: what are "trackbacks"...concerning posting to threads? Thanks in advance Neil.