A/C auto on

[RobsPages]

Hey guys.

It's 20 degrees outside and my AC keeps coming on when ever I turn the temp control to defrost the windshield. If I leave the dial on one of the defroster settings, the AC comes back on when I start the car.

Is this normal? Isn't it bad for the compressor to be on in such low temps (below freezing)? If it is on purpose, what's the point?

Thanks,Rob

[Concord]

Its completely normal. It keeps your windows from fogging up

[DUCeditor]

Yes, it is normal, and not just on the Versa.

They "why" is simple. Air conditioning removes moisture from the air. If one does not need the cooling one can simply reheat the air with the heater core and that makes it drier still.

No, having it on in cold weather won't hurt it.

What is unique to the Versa among the newer cars I have driven is that one can choose to turn the AC off. On even Nissan's XTerra that cannot be done.

Another nice thing about the Versa's air system is that the windows can be kept mist free in most circumstances with the central vents because these link to the rearward dash vents.

[biggie]

Just turn it off if you are not defrosting. I run just heat to my windshield sometimes and the AC isn't needed to remove any inside fog.

[RobsPages]

Thanks for the info.

Rob

[frankoV]

the auto-on also means that you don't have to remember to turn the a/c on every once in a while to keep the seals

[Slither]

I just find my compressor really 'buzzy' when running in this mode and at this time of the year in the cold weather. Same with the Sentra I had before but more pronounced on the V.

Doesn't make this noise in the warm weather when the a/c running.

Thoughts anybody?

[dewluca]

I understand why the AC should be on while defogging, but mine is NOT on then (at least according to the little light). The light on the A/C button turns on when I switch the control FROM the defogging settings to the main vent setting (the one at 12 o'clock). Is this also "normal"?

Brand new 2009 Versa Sedan 1.8S

[dewluca]

Finally found where this "normal" behavior is described in the owner's manual (pp. 4-4 through 4-7 in the 2009 OM). I'm guessing that the fact that they repeat the information several times on these few pages means that it is counter-intuitive enough to cause many people fits . . .

My only excuse is I've only had the car a couple of weeks and today was the first day I used the defogger . . . I guess tomorrow I'll bring the owner's manual in from the car and read about all the other odd behaviors I need to start accepting as "normal" . . .

[NODES]

Finally found where this "normal" behavior is described in the owner's manual (pp. 4-4 through 4-7 in the 2009 OM). I'm guessing that the fact that they repeat the information several times on these few pages means that it is counter-intuitive enough to cause many people fits . . .

My only excuse is I've only had the car a couple of weeks and today was the first day I used the defogger . . . I guess tomorrow I'll bring the owner's manual in from the car and read about all the other odd behaviors I need to start accepting as "normal" . . .

Leave the manual in the bathroom, you will be a Versa Expert in no time

[kc5f]

All three of our Versas have the compressor and A/C light come on as soon as you select either of the two defrost settings or start the car with it already in either of these positions, and it will stay on in any position until you turn it off with the A/C button or turn off the engine. I do like, as others have mentioned, that you can turn the A/C off even while you have defrost selected.

[dewluca]

All three of our Versas have the compressor and A/C light come on as soon as you select either of the two defrost settings or start the car with it already in either of these positions, and it will stay on in any position until you turn it off with the A/C button or turn off the engine. I do like, as others have mentioned, that you can turn the A/C off even while you have defrost selected.

Apparently the different model years behave differently? I'm attaching the explanation from the 2009 manual.

.

So, according to this, you cannot turn off the AC when in defrost mode . . . but at least now I know that what I thought was a defect is actually "normal" behavior

---2009 Versa Sedan 1.8S ~240 miles

[kc5f]

Wow - now I'm glad I got a 2008 in August instead of a 2009! That is quite a change from 2007 and 2008, where you can turn off the compressor but keep the air going to the windshield. When it's raining lightly outside sometimes I find that running it that way and keeping a window open just a bit is the best way to keep the windshield clear without running the compressor all the time and using more gas. But you're right - at least now you know yours is working as designed!

[NODES]

I believe the reason for this was also done as a "safety" how many retards do we see driving with their windows all fogged up and you cannot see inside their cars...how are they suppose to see out?

[Shad0wXCalibur]

Normal operation as has been said. I don't find it an issue because not only does it keep all my windows clear, it keeps it from feeling humid inside (which is what forms the fog on the windshield in the fist place). Anyone wanting to disable it because they don't want to expend the gas, how are you determining that it's using enough gas to make an issue out of it? I always let the a/c stay on in defrost mode and always use it in warm or hot weather. I also always average 30 mpg mostly city driving...

[kc5f]

It's not a matter of disabling it. Once the windshield is clear I turn it off. If it fogs up again I turn it back on. I don't know how much gas it saves, but if it saves any and my windshield is still clear, that's good enough for me.

[VersaMG08]

So basically, Nissan made the 2009+ model stupid proof when it comes to defogging?

[dewluca]

So basically, Nissan made the 2009+ model stupid proof when it comes to defogging?

I don't think this is about consumers as "smart" or "stupid", but rather the general trend these days for manufacturers to make decisions FOR consumers (see the defaults on any Microsoft product for numerous other examples) . . . (and often the manufacturers are the idiots).As someone who has lived in very cold, dry climates where it's defrosting of the outside of the windshield I need (first thing in the morning before I even get in the car to provide the only humidity for hundreds of miles), not defogging (which only occurs occasionally when I'm hot and sweaty getting in a very cold car), I resent the notion that I am incapable of figuring out when the car needs dehumidifying . . . (Not to mention how much strain the engine is already undergoing starting up in these climates without asking it to also run the AC . . .) . . . so making it impossible to turn off the AC when defrosting/defogging seems like a problem in these conditions.

I can live with this now that I know it is "normal" for this car (though we'll see how much complaining my car does this winter when I forget to move it off of defrost before trying to start in subzero temps), but I refuse to believe that Nissan "knows best" . . . (see the discussions of the placement of the Hazard Lights button over on the passenger's side in some models for more evidence). Just because a designer made it that way, does not necessarily mean it is logical or rational . . . or "for the best" . . .

[versa-medic]

So here's a new take on this topic, let me know if any of you have come across this:

When I first got the car, the compressor would turn on with the defrost, but the A/C light wouldn't come on. I know this is normal, and I read it in the manual and everything, and I'm completely fine with it.

Well, today I got in and started to drive with it on that defrost mode, and my windows started to get fogged up really bad. Going to my pre-V days, I naturally reached down and pressed the AC button, and wouldn't you know it, it lighted up. So no, all of a sudden, I have control over if I want the compressor on with my defrost or not.

So a summary--the AC with defrost used to be always on-and now, almost 7500 miles in, I can choose if i want it on or not

Any explanations?

[Promise Land]

Defrost and foot/defrost will run the compressor regardless of you having the A/C switch on or off.

[versa-medic]

I thought so, but there is a noticeable difference if I turn off the AC, my windows will begin to fog up, then when I turn the AC switch on, they will clear right up fairly quickly.

I'm not really complaining, I pretty much run it with the AC going anyways, but it's just an oddity to me.

[Promise Land]

The primary function of the defrost kicking the compressor on is to run the system and lubricate the seals and compressor. Any window defogging is just an added bonus.