J RIDE 81

I think I know the answer to this question but does the AC compressor turn on when the AUTO temperature is used? If yes, does it significantly decrease your MPG?

Thanks in advance for your responses.

HiTEC

This has been discussed before. Yes, if you climate control is in auto the compressor will be on (even if it's 5F out). I live in the Chicago area myself, and I've kept mine in A/C off all winter and only but it in auto when I needed to dehumidify the air (which has been almost never). In respect to the MPG, I can't really answer that for you, but I figure if I don't need the compressor why waste the energy to run it.

Yes, you should probably run it once and a while in the winter to keep it lubed.

SouthernBoy

Yes, but it is cycled automatically as you might expect. As for a serious hit to mileage.. no.

GUMP

I never knew the compresser came on. I've been running in Auto for a year and half and never knew the difference. I consistently get 25-26 MPG year round. I just started to shut off the compresser based on the treads here, but I find it to be a pain in the ass. I just keep it in auto and let it do it's thing. Doesn't seem to hurt anything. On days like today though (70 and great!), I just shut down the whole system and open up the roof..

SouthernBoy

I use my manual mode most of the time. While I like A/C, heat doesn't bother me.. I MUCH prefer the hot weather over the cold. So my A/C tends to get used on vacation because the wife is along, or when we go out somewhere. Most of the time, even in the dead of summer, I just open the windows and enjoy the warm weather.

richrath

I have often wondered the same thing.... I virtually always use the Auto mode, and just set the temperature to blow warmer or cooler. I could swear when the car was new and it was summer, if I hit the A/C switch, I would immediately detect the compressor coming on, and also I'd notice a 1 or 2 mpg hit based on the MID. Not a lot, but noticeable.

When using auto, I definitely think the compressor cycles on and off, because the mpg hit is not noticeable. I get 24-26 on every tank, but I strongly believe it would be less if I used A/C more often than Auto. But I could be wrong. My basis for believing the cycle thing is that if the temp is kept stable for a while, I don't hear any extra sound from the engine compartment. But if I change it, esp. if I set the temp lower, I hear a new sound immediately which I assume is the compressor. After a bit, when the temp in the cabin reaches the setting, the sound goes away.

J RIDE 81

That's very interesting. So it sounds like the A/C compressor goes on and off depending on the temperature. My question is why does it come on in the first place if you're trying to heat your car? Is it to humidify the air?

SouthernBoy

The compressor does cycle when the auto setting is used.. I'm speaking specifically about warm weather use here. You can both hear AND feel the compressor clutch and declutch when using the auto setting. In the manual mode, it will run constantly.

BrandonClaps

de-humidfy

Brettg

No matter what you do with it, if the ac is enabled, the compressor cycles on and off based on pressure.

You can run the auto mode without the ac, and the car will remember you have it off, so there is no need to keep turning it off if you do not want to run it.

In cold weather, the compressor will not run much.
In some conditions, you need the compressor to remove the humidity that will fog up all the windows.

The ac system will typicly cause less drop in MPG then opening the windows, at least at speed.

Brett