Air Con Operation

[Roker]

I have had my Corolla a year now and cannot figure the logic behind the air con 

If I have it set on automatic I would expect if I set the temperature high (above outside temp) it would switch heat in, and if I set the temperature low (below outside temp) it would switch AC cooling on , but it does it's own thing and the AC can be manually switch on/off

[dannyboy413]

My previous Corolla, (2021), and Yaris Cross, (2023), together with the current C-HR were/is the same. If I set the AC to Auto, it is as though the car is saying "Ha, I'm in control now, I don't care what you have set the temperature to, I will decide what temperature you are getting".  To be fair, I have never really bothered trying to get the better of it - yet!

[Roker]

20 minutes ago, dannyboy413 said:

My previous Corolla, (2021), and Yaris Cross, (2023), together with the current C-HR were/is the same. If I set the AC to Auto, it is as though the car is saying "Ha, I'm in control now, I don't care what you have set the temperature to, I will decide what temperature you are getting".  To be fair, I have never really bothered trying to get the better of it - yet!

That's the problem it doesn't take over 

[SDR]

I'm not sure about the Corolla, or Toyota cars in general, but I believe that some car auto HVAC systems have sensors that take into account more data than just the difference between the temperature you select and the outside ambient temperature, e.g. if you are in bright sunshine, possibly humidity, which alters how the system behaves. 

I don't really have much experience of using the auto setting in the Corolla because I usually operate it manually;   just because I prefer to, being an awkward SOB...

[TonyHSD]

Toyota does have all sensors and very advanced hvac systems.
They are always automated even in manual mode however if you select auto and AC on and temperature 22C° for example you can leave it like that all year around and it will do everything for you and it does work very well.

You can do manual mode and the system will do what has been asked to do , where to blow air, from where to intake air, temperature, fan speed. However even in manual mode the air flow temperature will remain automatically controlled with or without ac and after some time of longer driving 30min + the car will let cold fresh air from outside to refresh the cabin even if it’s freezing cold outside. 
When the car is off after a journey the hvac system remains active and does open and close its flaps to finish its stand by procedures. 

[TonyHSD]

5 hours ago, Roker said:

I have had my Corolla a year now and cannot figure the logic behind the air con 

If I have it set on automatic I would expect if I set the temperature high (above outside temp) it would switch heat in, and if I set the temperature low (below outside temp) it would switch AC cooling on , but it does it's own thing and the AC can be manually switch on/off

If you select AC off and auto mode when outside it’s cold the hvac system will not automatically select AC on. 
If AC is permanently ON and outside it’s cold the ac will still work but hot air will blow and the AC will dehumidify this air.

The best hvac settings on any car all year around are as follow: 

Auto mode ON 

Recirculating Off - this is automatically controlled by the ecu, however you can override when going through tunnels for example to stop smell and exhaust fumes enter the cabin 

Eco Off

AC On 

Temperature at 22° 

Set and forget. And change cabin filter every year or every oil service. 👌
 

 

[fred88]

I agree with Tony but I don't leave it at 22. Its probably a mood thing but if it's hot outside I'll set a lower temperature, if it's cold I'll set higher. Not logical perhaps but I'm human 😉

In the main a number of factors will effect cabin temperature and what needs to done to achieve the required temperature. The car has many sensors that help it determine how to do it.

In all my cars with aircon, or significantly Climate Control, it can be a bit of a mystery as to what it's doing. Just let it do its thing or tweak the set temperature a bit is my answer but always in Auto mode.

[Red_Corolla]

It does it's best to maintain the set cabin temperature irrespective of whether you've activated the A/C or not. You turn the A/C on or off depending on whether you desire the effect it has on the humidity or not, keeping in mind that the system may not be able to achieve the set temperature without it while it's hot or sunny out. It does take over when you select demisting, otherwise you are in the driving seat (pardon the pun). As someone who doesn't always want to sit in dried air the whole time, I think it's a good system. I only ever touch the A/C button - I never feel the need to adjust the temperature away from 21.5, all year round.

[Chuffmonkey]

I don't have an issue with the aircon, left on auto and eco all year round. In the winter ill turn the temp up and its nice and warm, in the hot weather (when we get a nice day) Ill drop it to 18 and it cools the car. I think it does the job pretty well.

 

[Eddiefh]

20 hours ago, TonyHSD said:

If you select AC off and auto mode when outside it’s cold the hvac system will not automatically select AC on. 
If AC is permanently ON and outside it’s cold the ac will still work but hot air will blow and the AC will dehumidify this air.

The best hvac settings on any car all year around are as follow: 

Auto mode ON 

Recirculating Off - this is automatically controlled by the ecu, however you can override when going through tunnels for example to stop smell and exhaust fumes enter the cabin 

Eco Off

AC On 

Temperature at 22° 

Set and forget. And change cabin filter every year or every oil service. 👌
 

 

Hi , not sure I fully understand with this if you set at 22 won’t it be warm in summer I normally set mine at 22 in winter or I’m obviously not understanding? 

[Mike Manthe]

Roker,

I have a different problem. My 2017 Highlander the gas gauge doesn't work properly. When it says I'm low, if I add a gallon, it still says low. Add another gallon and sill low, add a third gallon and suddenly the gauge shoots up to ~3/8 full. The dealer could not fix it. 

Mike

[fred88]

Well that's a conversation stopper!

[TonyHSD]

12 hours ago, Eddiefh said:

Hi , not sure I fully understand with this if you set at 22 won’t it be warm in summer I normally set mine at 22 in winter or I’m obviously not understanding? 

Hi,

It’s not gonna be either too hot or too cold during all seasons because the car will automatically manage the pre set temperature using air conditioning and heating from the engine. 

22C° in car cabin has been the ultimate pre set temperature for any hvac system in any car. Once set correctly, you never need to do anything anymore and if sometimes you ever feel cold or hot you only need to adjust temperature up or down by 1 or 2 degrees and the system will respond and start blowing hotter or colder air accordingly. 

The AC should be kept ON all the time to enhance the whole process.
For most people ac cold and dehumidified air it’s not noticeable when ac is permanently on , for those who has health issues or simply does not want ac on permanently then they can use hvac in manual mode which still gonna maintain temperature automatically but without engaging the AC , this was the OP question originally. 

 

[Eddiefh]

1 hour ago, TonyHSD said:

Hi,

It’s not gonna be either too hot or too cold during all seasons because the car will automatically manage the pre set temperature using air conditioning and heating from the engine. 

22C° in car cabin has been the ultimate pre set temperature for any hvac system in any car. Once set correctly, you never need to do anything anymore and if sometimes you ever feel cold or hot you only need to adjust temperature up or down by 1 or 2 degrees and the system will respond and start blowing hotter or colder air accordingly. 

The AC should be kept ON all the time to enhance the whole process.
For most people ac cold and dehumidified air it’s not noticeable when ac is permanently on , for those who has health issues or simply does not want ac on permanently then they can use hvac in manual mode which still gonna maintain temperature automatically but without engaging the AC , this was the OP question originally. 

 

I’ll give it a try later on  , thanks 

[TonyHSD]

39 minutes ago, Eddiefh said:

I’ll give it a try later on  , thanks 

Definitely try it and I am sure you gonna like it , it might be strange first set and forget but these systems are smart enough and they do everything for you. 
Just make these settings 

22C° - Set temperature 

AC ON 

Recircluating off

Auto ON 

And leave it like that. 👌

[Corolly Poly]

38 minutes ago, TonyHSD said:

Definitely try it and I am sure you gonna like it , it might be strange first set and forget but these systems are smart enough and they do everything for you. 
Just make these settings 

22C° - Set temperature 

AC ON 

Recircluating off

Auto ON 

And leave it like that. 👌

I'll give this a try. Earlier you said Eco = Off but others have said On. What's the difference?

[TonyHSD]

36 minutes ago, Corolly Poly said:

I'll give this a try. Earlier you said Eco = Off but others have said On. What's the difference?

Eco off and eco drive mode off too. 
Drive mode best is normal and hvac settings in normal, no eco , no fast. 
AC should be on all the time and recirculating off , the later may come on or off as per the hvac ecu control . 
The difference between hvac eco on or off will be the ac engage time and power. Saves perhaps 2mpg but messes up your comfort. 

[Trewithy]

I have my CC set to Auto and 21.  22 would be too warm for me in the winter. 

[AndrueC]

The idea of keeping the same temperature all year round seems reasonable until you consider the clothing people are likely to be wearing.

In winter I'm typically wearing long trousers and a jumper. In summer it's shorts and just a tee shirt.

Therefore during the winter I have my car set to 19.5c and in summer it's set at 21c.

But I don't understand why there's anything confusing about the operation. You choose a temperature and the car does what it can to maintain the cabin at that temperature.

[fred88]

Normally if jump in a car that's hot having been parked in the Sun I'll wack the climate temp right down and then edge it up.

Today I decided to try the advice on this thread and just leave it at 22. It was fine, nice and comfortable in not very long at all.

I think too many of us, myself included, suffer from aircon paranoia, feeling the vents and concluding that it's not cold enough. The real measure, particularly with Climate Control, is does it maintain a comfortable temperature / environment. If it does, don't worry.

[TonyHSD]

Many people has issues with car hvac system because of misuse and misunderstanding how the system works and they do intervene wrongly which makes things worse. 
The best way is set and forget. 
The AC , some people doesn’t like it, they claim they have health issues. 
I can understand that and this is why there are options to over ride , turn on or off. However more you play with the system, more issues you can have, including bad smell, moisture, wet windows, etc.  

Tips for all. 
if you  gonna use ac just keep it on all the time. 
If not use ac, keep it off all the time- no need to run just because to keep it working, these are myths it will get problems if not regular used. 
Do not turn off AC few minutes before arriving at your destination, this will make your car smell bad. 
Once you had made all correct settings and if for some reason you feel a need of extra heat or cool air just adjust temperature settings up or down by 1 or 2C° and the car will respond accordingly. 👍

[Rhymes with Paris]

Does that apply to ordinary Aircon Tony?

As in the kind on my old Yaris,as opposed to climate control such as was on my CRV which did everything automatically,in fact it was difficult to turn it off altogether, maybe that was the idea, meant to be on all the time.

As a pp said about aircon paranoia though, it reminds me of the hottest, stickiest night round here for a long time,a few years ago.

In my old lexus, I went to pick up my hard of thinking pal to go to the metropolis of Newark for a BBQ, you know the type where they mug you for the good stuff you have brought, and you finish up with half frozen, half burnt sausages and burgers from dubious sources.

Anyhow, upon picking up my paranoid pal he immediately started squawking about the aircon being on, and how it would kill him if left on for a half hour journey.

Turns out he had someone read out loud to him an article about how someone in a air-conditioned building many years before, had contracted legionares disease, and so we sweated our way there and back.

This was the same fellow though,who was convinced by a brainwashed TV programme that the moon landing in 1969 was faked.🤔

[AndrueC]

A car HVAC system is unlikely to harbour Legionnaire's disease. LD bacteria lives in water and car HVACs don't have enough water(*) to harbour them.

Most smaller HVAC systems are compressor based and collect the condensate and dribble it onto the output coils to slightly increase the rate of cooling but it's rarely large amounts of water and typically evaporates between uses so LD would die. It's also fairly unlikely to enter the target space since the resulting water vapor is blown out of the exhaust hose. This is why modern portable A/C units shouldn't need draining. I can run mine for six months and when I pack them away the condensate collection tray is always dry as a bone.

I have no idea if Toyota's HVAC uses the condensate in this way but I doubt it. The puddles under the car after A/C has been working hard tend to suggest not.

A system that is evaporation based is more risky. I don't know if these systems are still in use today but some of them blow the water through a curtain of water to cool it down. Such systems could certainly harbour LD and if they did would be blowing it straight at the people being cooled down. It's possible such systems have been banned.

[TonyHSD]

Yeah, all suggestions above will apply to all hvac systems, newer or older cars. 
The main difference between older turn knob ac only system and more modern climate control is that temperature is not automatically adjusted  and the air flow and speed , all settings needed to be adjusted  by the driver to maintain let say room temperature. 
My previous car with manual hvac I was doing exactly all that.