AC Recirculation

Are you in ECO mode too? I stay in ECO mode, and auto climate on, and it does stay in recirc a lot. No problems so far, but it's only been 8 weeks.

 

I have, just once, weeks ago before it hit 90-97 here during the day.

 

I use ECO mode all of the time, and have seen AUTO set it to "fresh" quite a few times. I actually can smell the difference, so maybe that's why I've noticed it. It happens most on longer trips.

 

Leaving it in recirc for too long is what causes the mildew smell. Switch to outside once in a while if it won't do it because of weather condition.

 

I leave mine on recirc 90% of the year because: a) cools/heats more efficiently, and b) allergies. If I'm willing to have fresh air, I'll open the windows and really enjoy it. The only real issue that I can think of with perma-recirc might be humidity if you drag a lot of moisture into the car (say you're wet from rain) and it can't escape. But I could be wrong.

 

I think the Toyota engineers have thought about this too. I could not get any confirmation in the Prius manual about this, but I suspect recirculation is not 100%, they'll still let a tiny amount of fresh air in to prevent the driver from getting drowsy.

I have driven a Mercedes A-class in the past and it automatically disabled recirculation after about 20 mins. Also to prevent drowsiness.

 

I remember reading somewhere that most cars when set to recirculate will still bring in about 10% outside air to prevent staleness. Makes sense to me for many reasons. If you drive through smoke while on recirculate it doesn't take long for you to smell it.

 

Keeps the new car smell in the car longer, but Toyota's new car smell isn't that strong to begin with

 

I have my climate control set on auto and the car often switches to 'fresh' when I don't want it to. For example, my wife has allergies now so we'll push the pollen filter button, which filters the air in the cabin for 3 minutes. This is supposed to reduce the amount of particles floating around the cabin. But often when the 3 minute period of filtration has finished, the car goes back to 'auto' mode and promptly switches the air source to 'fresh', bringing into the cabin whatever pollen is floating around out there, which in my mind defeats the whole purpose of using the filter. So each time I push the filter button I have to watch for that 3 minute period to pass so I can switch the source back to recirculate after the car decides we need 'fresh' air. Anybody else notice that?

On my previous car the fresh or recirculate switch was manual. I drove that car for 5 years with the air source set on recirculate all the time. The car does not get stale, that car (corolla) wasn't that airtight to begin with. Mildew does not build up. The recirculate feature reduces AC work in the summer and it also reduces the amount of exhaust you smell when driving on freeways. It also keeps that new car smell for much longer. One point though, at least on the Corolla, when you set the mode to front windshield, recirculate is not an option.

 

Going fresh air after your 3 min filtering period should not do any harm, as the same filter is still used to clean outside air. My understanding is that the recirc-filter button simply turn the fan higher, goes recirc and clean the inside air more quickly and efficiently. From what I've read in other threads, this feature is almost mandatory in Japan as most of the population have allergies.

Also, the inside air in recirc won't become humid as the A/C removes moisture (recirc or not).

Beware that the nice new car smell is made of VOC (Volatile organic compounds) ([ame="http://en.wikipedia.org/wiki/Volatile_organic_compound"][/ame]), mostly from adhesives/vinyls/plastics. VOCs are known to be carcinogenic, that is why Toyota is making efforts to remove those compounds from their cars (I believe the new Prius is the most advanced yet on this front). In my case, I often switch to outside air (I'm in ECO mode all the time) specifically to get rid of the VOCs/new car smell.

 

Thanks. I guess we have to choose our poison. I have to commute about 15 miles on a major highway full of traffic so I like to use recirc hoping to reduce the amount of exhaust I breath. Definitely can't smell the exhaust as much which might mean we're breathing less of it. If I was driving less traveled roads I'd have that fresh air coming in though.

 

Recirc is not 100% recirculation unless you have the dealer change the internal setting (used in very cold climates). This means some fresh air comes in even with recirculation.

Moisture isn't a problem unless you turn off the A/C compressor. The A/C compressor is used as a dehumidifier when conditions call for it.

The musty smell some get comes from crud in the A/C evaporator and is not related to recirculation, but simply to the use of A/C. Recirculation does not make this better or worse, unless mold is growing on your carpeting.

Tom

 

I bringing up this thread again because I wanted to make a summary of when and how is the recirculation activated and I am a bit puzzled still today about the functioning of the climate control in Auto mode in winter (with outside temps around 0C).

So to summarise:
1) When Auto is set, recirculation will be enabled by the system when in ECO mode, even for long times, but in high temperatures
2) When Auto is set and temperatures are around or below 0C/32F, recirculation is not set, even when in Auto and the A/C compressor is not used even if the A/C light is on
3) ECO mode will slow down fan and reduce A/C effectiveness in warm temperatures, will reduce the fan speed and the time the ICE is turned on when in cold temperatures (if you are at a traffic light, the engine is on in normal mode and it is not warming up, if you press ECO the engine is shut down promptly - tested it several times).

Questions:
a) when Auto is set, and the car is turned on "from scratch", recirculation is turned on if the interior cabin temperature is very high (to cool faster)?
b) why is recirculation not turned on in winter to warm the interior of the cabin faster? is there a humidity sensor for outside and inside air for the system to understand what to do or is it taking decisions only based on temperature?

Here in Munich it is now anything between -6C to 0C, I drive mostly in ECO for the reason explained in number 3 and the Auto sets the air always in the air flow to feet and "windshield defogger operates" as per page 273 of the US manual; what does exactly "windshield defogger operates" means, compared to the "mainly air flows to the feet" mode on the same manual page, I don't understand, since there are arrows coming out from the windshield vents in both cases on the pictures...

Bottom line: assuming that the cars in front of you are not stinking (or similar situation), can you have the climate control set to Auto and with A/C on (light on) and be in a "set and forget it" mode? will the system use air recirculation effectively to get the best result with minimum effort? will air recirculation work automatically also when driving in normal mode or do I have to take care of it?
I.e. when turning on the car after it stayed under the sun? - the Honda Jazz/Fit of my parents does that automatically for a few mins, my Polo used not to do that - obviously I will drive for 1-2 mins with all windows open to make sure the extra heat, compared to "outside", gets normalised and the outside air can actually cool down to ambient temperature the overheated plastic/seats/interior (cabin temperature under the sun is always way above outside temp)

I would like to avoid fiddling with the commands depending on the temperature and the humidity outside.... after all that is why there is an "auto" button... How smart is the climate control of the Prius???

 

If I remember correctly: yes (summer seems to be very far from now...).

It avoids recirculation to prevent frost on windows. From what I've read, I think its decisions are in fact only based on temperature (no humidity sensor).

 

I don't know the answer for this with the Gen III, but with the Gen II Prius recirculation mode is not 100%. There is a dealer settable option that can force it to 100%, but that's not the standard. It was offered for those living in very cold climates.

Tom