AC Compressor FK8, ON When Using Heat?

[DRKSYD]

Hey,

Searched for a little bit while watching the Packers barely win today...and didn't see anything that clearly defined this car. (2019 FK8)


I noticed that the AC compressor is engaged when the heat is on. If I go into the climate screen and turn AC to OFF, you hear/see idle drop slightly. ...But this is when the car is in heat mode or should be heating. It heats but is this trying to heat AND cool to maintain it? (leave the compressor engaged/on for quicker response?)

I understand it's climate control in auto mode, but I wouldn't expect the compressor to be engaged until it needs cooling. Played around with it and it does it at any temp. set-point, when it's not actually cooling.

Defrost is not on which I would expect to turn the compressor on but you shouldn't have to manually go in and turn AC to OFF, when climate control is turned on. For that matter, neither ON or OFF are "lit" up on the display until you select one of them.

Posting as it's drawing a load on the engine for something not needed. Just want heat, not heat plus the compressor always on to cool.


Thoughts?

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[RedGiant217]

Running the AC compressor helps keep windows from fogging as it will keep the air in the car pretty dry.

It's obviously not necessary to leave it on, but I think it would be pretty common for it to be on in auto climate mode.

EDIT: Note that the fan speed will still be automatically controlled if you were in auto climate mode and just switch the AC to off.

 

[ez12a]

AC serves a dual purpose, to cool and to dehumidfy. When used in conjunction with the heat in cold weather, it will keep your windows from fogging as mentioned. Might seem counter intuitive, but blowing only warm, humid air at your windows wont dry them on the inside. It also keeps the interior of the car warm, and not stuffy for your passengers.

Pretty much how any defrost mode in a car works too unless you manually toggle A/C off after enabling defrost.

 

[DRKSYD]

Ok..... I understand defrosting windows but that should be part of the defrost cycle and I don't usually need defrost. Compressor shouldn't run nonstop. That's a waste of power and energy.

My point was. . Why is it running all the time? There isn't a manual only option. You set a temp. And the system runs. You shouldn't have to turn on heat, go into climate control and shut of the Ac... Like I said. It's technically not even showing as on at that point

 

[ez12a]

Any time you press Auto for HVAC in a car, at least in the Honda and Lexus vehicles i've been in, A/C will be on regardless of cooling or heating.

technically it shouldnt run non stop. Should cycle on and off as necessary.

There is manually only option, you just have to hit the climate button and and adjust fan speeds..manually. Although at least in my 2018 I've noticed if you turn the HVAC off and turn fan on again manually, A/C is automatically enabled again.

Workaround is to never turn the fan off. Just turn it to low and leave it, adjust fan speeds and thermostat as necessary, which still works with Auto disabled. As long as you dont shut it off and turn it back on, or hit the Auto button, or hit the A/C button, it wont start the compressor.

 

[fk8mike]

also a/c working on winter keep the compressor working for years i mean less suceptible to broke

 

[remc86007]

I guess it depends on where you live, but here in Florida, when it is cold enough to use the heat, if you ran the heat of an extended period of time without A/C, eventually the windows are going to fog up and it's going to be really uncomfortable in the cabin because of the humidity buildup. These relatively low draw compressors in new cars are a godsend because it's no longer a big deal to have the thing cycling on and off just to keep the cabin comfy.

I wouldn't be surprised if these cars have a humidity sensor and only cycle as often as needed.

 

[02SilverSiHB]

yeah, I've been in all kinds of cars...all run A/C with the heat automatically to avoid fogged windows

 

[jasonjm]

The air conditioner also acts as a dehumidifier, preventing windows from fogging up. Hot moist air inside reacts with a cold window being cooled from the outside. Creating condensation. Remove the moisture, remove the foggy windows.

Feel free to turn it off if your climate does not necessitate the use of the compressor.

 

[FK8_K20c1]

Disagree with most comments based on my experience. i manually turn the AC off when I press on the front windshield defrost option that I use to keep the car warm or a litttle cool during winter and I do not experience any windows fog as long as the recirculating vent is open.

 

[DRKSYD]

Disagree with most comments based on my experience. i manually turn the AC off when I press on the front windshield defrost option that I use to keep the car warm or a litttle cool during winter and I do not experience any windows fog as long as the recirculating vent is open.

I don't usually need the compressor on to defrost windows either. Just the warm air moving over it is enough. Also, AUTO isn't on, just normal heat, which automatically has the compressor engaged. Doesn't make sense to have an auto mode where you have to go in and shut the AC off...when using manual mode.

This is always while using the front vents/floor vents, not the defrost one.

 

[Deleted member 31314]

Recirculating the air would probably be enough in most climates, the colder the air though the bigger the difference. I am in Canada, where I live now sometimes I use it on auto and other times I don't. But I grew up in Winnipeg (or Winterpeg) where extreme cold and moisture could be problems so the a/c + heat works wonders, that was before auto settings thought where you set up how you wanted the car to run before you turned it off lol.

 

[repeet]

Our tenth gen Civics have a variable vane, variable demand compressor. What happens in the winter is that the compressor will engage all year long and keep the internal seals from getting hard and cracking. The main reason for "leaking" Freon.

Also being variable vane, it's suppose to throttle back and shed the load on the engine when you WOT. Somewhere years ago I think I heard that it will throttle back the compressor during any acceleration.

But yeah, when I "hoon" around I fully turn if off. Also If I'm trying to hyper-mile it. The rest of the time I let it spin happily while it keeps itself lubed and healthy.

 

[ez12a]

I agree that ac mode off or on should persist when turning the fan on or off independent from Auto. I thought it was weird it didn't remember but got used to it by never turning the fan completely off. AC won't automatically turn on even when you restart the car.

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