General AC question

I wondered about this myself a few months ago so I looked at my manual. I wanted to know which setting used the compressor.

Normal AC takes air from outside the cabin and cools it. The air outside might be very hot so it takes a lot of cooling to bring the temperature. Max AC cools and recirculates cabin air. That means that it is further cooling air that it has previously cooled but it also means you aren't getting much fresh air in the cabin. Use MAX AC when you first get in and the cab is blasting hot then switch to Norm.

Max AC and Off are the only settings that don't bring in outside air. This is handy if you get behind a smoking truck, run through a dust cloud or most importantly travel through an area recently visited by a skunk or past a mushroom farm. It's not recommended to use MAX AC or Off for long periods of time because the cabin air can become stale. I haven't really found this to be true with Max AC but I have for Off.

Off, Panel and Floor are the only settings that do not use the AC compressor. Panel+Floor does. So if it is cool, you might save a few farthings on gas by using those settings. Most of the time it's probably not worth it since AC tends to keep the windows clear.

Stephen

That depends on where you live. Here in SC when it's 95 degrees out with humidity to match, it's best to start with outside air, then move to max air after a few minutes. The temp inside my car has been 150 in the full sun, and trying to cool that rather than the 95 degree outside air is pretty futile. Just my $.02, FWIW.

SC Tom

Alright, thanks guys!! I've actually wondered that for years, and just kept forgetting about it when in front of this thing until today! It's one of those things that's not important enough to be hell bent on an answer, but something just to satisfy curiosity!

Once again, thanks,

Doug

some vehicles actually speed up the fan on 'MAX', but on some it just SOUNDS faster cause the fan noise is ducted back intothe cab on the intake side

I think it might have something to do with cab air pressure. I took the back seat out for trip this month and I discovered something kinda interesting. Of course there was more road noise without the seats and seat backs but the cabin vents at the back of the cab were exposed. They are small rectangular openings with sort of louvres made of flexible material.

Cab pressure drops when MAX or Off is used, which makes sense because you are not forcing air into the cab. You can actually see this as the vents are open with most settings and closed on MAX and OFF. With nothing to slow the increase/decrease in pressure, you could also feel your ears pop when switching back and forth.

So...I speculate that maybe when you switch to MAX the fan has less resistance, that is, that it is not trying to stuff more air into the cab and increase pressure so it speeds up a little.

Stephen

TranSurge> some vehicles actually speed up the fan on 'MAX', but on some it just SOUNDS

I noticed the pressure on my ears when I switch from MAX to just AC in my Ranger. I never noticed that in other cars. I'll have to take my altimeter with me to see how much pressure change there is. John