When I use the auto climate control, I don't know if the A/C is coming on and reducing the MPG. I know that if I set it to 68 degrees that the A/C is coming on, but what if I set it to 73 or 75 degrees? Are there any settings where the A/C turns on and off intermittently?

 

All of them. The AC will only run as needed, and won't pull full power if it isn't needed. That said, I prefer to just use my windows in summer, and leave the auto-control for winter.

 

I would use the windows too, but I read an article where they did a scientific study and stated that the drag from open windows causes about the same decrease in MPG as using the climate control.

So if I set the temperature at 73, then the A/C compressor will turn on and off as needed? And if I set the temperature to 77 on a fair day then it may not come on at all, right?

 

If you press the A/C button it will toggle between A/C Off , A/C ON, and nothing. With nothing showing, the A/C will come on as needed. With A/C On it will be on and with A/C Off, it will be off. I usually just shut the whole climate control off but if I need heat, I wlll make sure it says A/C Off.

Just to confuse it more, no matter what it says regarding A/C, if you have the mode set to a defrost mode, the A/C compressor will come on as needed.

I really would prefer an old manual style of climate control like my 92 accord. The A/C compressor would never come on unless I pressed the A/C button and then it clearly showed it was on with a iight.

 

I think unless you SEE the message A/C Off, it IS subject to come on as needed.
In AUTO, you don't see the message A/C On, yet it comes on as needed.
With message A/C On, it's really on - all the time.

Auto seems to work best for my MPG. I think others (those that use A/C) agree.

Plus, it ALWAYS comes on with defrost.

 

I made a few mistakes dealing with the AC in the hot Texas summer.

First, I had it coming out both bottom and top vents. Just use the top vents, as thats where the heat is at that needs cooling. AC had to work harder going out both vents. Took a lot longer to cool off the car (and battery)

With 100F days, I had it set for air from outside to come in. Not good, trying to cool that hot air from the outside. I was thinking that I would improve the mileage, but was causing it to be worse.

I use to set it for Auto, but have been finding that if I set it to low (all the way down) its easy to turn it off in the morning commute when its not too hot, and on for the late (hot) afternoon commute. I leave the vent to the outside open for the morning, and closed for the afternoon. If its on Auto, you can't set it for the fan only, which is about perfect in our mornings with the vent open.

This has really made a good difference in my mileage, after getting some really low to mid 40's, now I am back into the upper 40's to 50 mpg per tank.

I will also leave the windows down a little in the afternoon till I am on the freeway, (a few miles) with the AC off, but vents open and fan on. Once on the freeway, then kick on the AC, close the vents and roll up the windows.

I am sure it all varries, depending on where you live, your temps, and your commute. You guys in Canada are probably already dealing the heater...while its still about 35C down here in TX

Bob, 2006 HCH (Nov 2005)
N5KF

 

When I do use my A/C, I prefer to use vent (outside) air first... at least until the inside has cooled to the same temp as the outside. Then I switch it to recirculate. This makes more sense, since it's easier to cool the 95 degree outside air than the 140 degree inside air (guessing at inside temps with a closed-up car in the hot sun).

Unfortunately, when I use "auto", it almost always puts it in recirculate mode from the start. That's one the engineers must have missed. If inside temps are warmer than outside, it should use vent first!!!