AC is "on" when turned "off"?
 

I have noticed that when I turn my AC off, but my temperature to "coldest" I can still feel AC coming through windshield vents in the "windshield-vent" mode. When I turn the vent dial mode to other vent modes, I do not feel the AC anymore.

Yes, I'm sure it's AC coming through in windshield-mode. How do I know? In windshield mode, it's super chilly air, "AC-like". In every other vent mode, it feels like "normal" air, that isn't chilly.

Why is this happening? I have no idea, I would think AC and vent controls are not interconnected.

This concerns me, because I don't want to burn up extra fuel to support AC when I don't necessarily want AC. I haven't taken this in yet, but I wanted to see if anyone else could recreate this also.

When you set your selector to any setting that includes the windshield, A/C automatically comes on. Most newer cars do this.

Hmm... I'll have to check my '11 Forester XT, but I had a '11 Ford Fusion, and I don't remember it doing that.

It's designed to defog the front windshield. Newer Toyotas do that.

got the same on my 07' 350z, most newer car do this. However, its also noted in the Drivers Manual, so RTFM :-)

You might be able to deactivate this by holding certain buttons on the A/C unit, and/or turning the key to a specific setting.

It will take time before anyone learns these codes though, eventually someone will post them if it's possible. It worked for my Acura, now I decide when the compressor comes on. Actually it still works as designed, but now I have the ability to turn it off by pressing the button.

So, where do these little bits of knowledge come from? Shop manuals? Service manuals at the dealer?

I'm sure you can "disable" it by setting the temperature to a bit warmer. That's what I do in my GTI...

My NC MX5 automatically turns on the AC (if switched off) when I set it to defog the front windshield.

A/C mode turns on when used for defogging because a/c air has less moisture in it than regular cabin air.

Even with the heater the AC system will run in a defog setting.

Most, if not all, new cars do this as already stated. In many cars you can easily disable it, in some, it requires a bit more work.

atleast you have a premium so you have more control over when the a/c comes on vs the auto climate control in the limited models.

The AC runs because it also removes humidity from the air.
Humid air on windshield = fog.

So if the compressor is running this often, then the car will be a bit down on power, because it's a tiny 2.0L engine and electrical stress does this.

What's the easiest way to knowingly turn off the compressor?

Just don't set it to any setting that shows the windshield/defrost on the dial.

Both of my other newish cars did the same thing.

The A/C is not just for cold air. The Air Conditioner is exactly that and the intended side-effect of the conditioning of that air is cold air (the act of removing the moisture). This is why the system runs when you click on defrost because the "conditioned" air is dry. In our nanny-state of driver aids this is automatic but for the older crowd here many were taught that when they used the defroster they should also turn on the A/C to actually defrost the windows. And yes, you can run the heater and the a/c simultaneously.

edit: it's my understanding that at high rpms the A/C compressor disengages for the sake of increasing its lifespan. Can anyone confirm this?

Sounds good to me guys, glad I checked here first!

I'd still like to know where these programming codes originate from. The first time someone posts them in a related car forum, where did that guy learn it? Someone should get the ball rolling, there might be quite a few some of you would like.

u can pull the fuse!

it's not to preserve lifespan, but rather to give you full power under WOT.

This is normal if you don't want fresh air to come in put the recyclin mode on.

Dumb feature. I disconnected the wires to the AC compressor about a week ago. Couldn't be happier.

It would be easier to pull the fuse...

The little gray plug on top the compressor is actually probably easier to disconnect and reconnect than finding the fuse ;)

Affirmative.

No. Recirculation is also disabled when in the defrost mode.

I leave mine set to the dot between the legs & windshield/legs options - and the compressor doesn't ever kick on, if I want it on I have the option by pushing the AC button.

But as soon as I switch it to windshield/legs or just windshield it kicks on.

LOLs.. but it's ok Pretty sure in Ottawa he doesn't need AC in summer. Miss the weather in canada, (K minus winter).

That's exactly what I do.

Actually, its 2 different features for 2 different objectives

1) The compressor disengages at high RPM, because the compressors are not designed to operate at full engine RPM.

2) It also disengages at WOT, regardless of engine speed. As you stated, this reduces engine load when you call for max power (WOT).

Holy thread necro.

Yes, yes, I hate it too since it bogs down the engine :(

From yesterday?

From 2012. This is a very old thread.

Would have made more sense if he quoted the original necro bump.

subbed!

Indeed it's an old thread. I resurrected it because A) it's completely relevant, and B) it's number one on Google if you search for "frs air conditioning defrost dumb feature"

Annoying that the AC light stays dark even though the compressor is running in defog mode. Where I come from, "off" means "off":confused0068:

Turns out my approach is imperfect: the condenser fan still runs.

lol

It is actually more beneficial for any refrigeration system to run on occasion then sit. It helps keep moisture out and the seals wet so they don't fail. I would hate to have to buy a new A/C compressor a couple years down the road.

Someone said something about electrical load. The only electrical load the compressor has is the small amount for the clutch, the rest is the mechanical load of compressing something to upwards of 400 psi.

The great part is everybody will disconnect it and then we will start getting all sorts of posts that say "windshield keeps fogging up what can I do?".