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-   -   A/C: internal circulation leads to stale air? (https://www.team-bhp.com/forum/technical-stuff/30136-c-internal-circulation-leads-stale-air-3.html)

An easy way to remove any interior stink is to place pouches of Activated Charcoal under seats, glovebox and boot. This can be bought of Grocery stores as Fridge Deodoriser or @ Aquariums selling submerged filters.

Well if you live in bangy, the amount of pollution outside will ensure you stay on internal recirculated air. Fortunately i drive alone and so I guess there's enough oxygen in my car to sustain for a few hours.
Mostly I switch to external air at high speed roads eg ring road or inside roads like drdo where there are lot of trees :)

Ofcourse on long drives one must ensure that the air is from outside as all cars release carbon monoxide (CO) in small quantities which is poisionous odourless colorless gas with a high affinity for oxygen in our blood (to form CO2) and this can cause a large number of health problems including death as seen in bombay floods (where people were on internally circulated air for hours)

So be careful and keep in mind that time to time you keep swithcing to external air when there is less pollution or open roads :)

MY A/C is set to recirculate: Always.

On a highway, when driving the windows go down once in a while.

usually when I feel like it and definitely when I cannot remember something like distance done, and have to look at the trip meter to remember it.

Any idea how much extra fuel is consumed in the fresh air mode (compared to recirculate mode).
Also how significantly does the engine power and acceleration change in both modes.
I find that in recycle mode the engine sound at idle seems different than in fresh air mode -don't know how to interpret it though.

Here is my understanding of the two modes, Benji : The compressor is going to function to bring the temperature to a preset level. So, if you have in re-circulation mode, you always get fresh air for the A/c to cool and it will be working all the time (meaning, running for the full cycle of ON - OFF, where the ON cycle is longer).

This is because the air coming in is not cool and the compressor is working at max to cool it. The status or working cycle time will not change because the air is always fresh and is always warm.

Now in recirculation, this above condition will happen during the start, but going forward the compressor will work at a reduced load, since the air is already cooled.

These thing translates to difference in load on the engine, because, when the compressor is not running, there is no load from the A/c on the engine which means more power in the engine and vice versa.

What will be good for quick cooling is, when taking the vehicle initially, it is best to run it in fresh air mode for 5-10 minutes and then move to re-circulation.

Yupp, I follow the same procedure and recommend it! Rolling down the windows every 20 mins or so for a minute or two will allow fresh air to recirculate in the cabin and keep your condenser box and cooling coils free from dust, leaves and other stuff that usually finds it way in thru the air intake vents at the top of the bonnet if you use the recirculation mode.

Cheers,

gpa

Sorry megger its not like that. Almost all split ACs (barring a few very high end ones) have no provision for recirculating fresh air. Its one of the biggest disadvantages of a split AC and of the least concern to most people. In day time use of these ACs there is not much problem as air change does happens every time the doors open (of course if the adjoining space is ACed too then it does not. However its more serious when one is using at night because by morning the O2 levls do fall. Its best to leave your window slightly open. In several places we do reccomend a small low power consumption fan (like the ones you see in the computer) to recharge fresh air. That works well.

Yes, thanks. I do understand more about ACs now :)

A Basic question..!

For A/C in fresh mode. Where are the intake vents of a car? Say an Alto or a WagonR?stupid:

In almost all cars these intakes are located just ahead of the windscreen - the grille or slats that you can clearly see!

I think the amount of air recirculated is different for different cars, some members have reported in this thread that they always use the recirculation mode, still find no problems, some even are able to smell external diesel fumes etc. on recirculation mode.

I can say that the Optra recirculates nearly 100% on recirculation mode, i cannot use the recirculation mode for more than 35 minutes at a stretch, I have to open the windows or use fresh air mode on the AC after that or i feel drowsy after that. The Optra has an excellent air/pollen filter though, one can use it on fresh air mode in Pune with no problems. I switch to recirculate only if there's some irritating kerosene gulping rickshaw or a coal burning truck/bus in front of me.

The important thing that one should not forget is to check whether you are feeling drowsy, that is a condition one should disallow at all costs.

Any idea what kind of A/c filter the Esteem uses? Any chance of changing it for a better one? Could not get any helpful info on this at the MASS. :(

Query : After how much time do you put your AC back into fresh mode ?

This would depend on factors like, the number of occupants in the car, conditions outside (smoke,dust,pollution) and also the ambient temperature prevailing at the time.

Cheers,
gpa

Adding to what GPA has mentioned, it also depends on how you want to re-fresh. I usually just bring down the window for sometime. This should refresh / move out the old air and bring in the new. But then, the concern here will be that one should do this only when passing thru some nice green area, without dust or smoke. :)