A tech at local dealership said the recirc setting was tougher on ac system then when drawing air form the outside, I can feel increased airflow and cooling when on recirc, BUT , i was thinking the air is already that much cooler and had moisture drawn out of it. So why is cooling air from outside car that is warmer and higher humidity easier on A/C system then recooling interior air. Do you leave your system on Recirculate often in summer months. THanks for the information.

Rebreathing the same air for any significant length of time will decrease the efficiency of the driver by reducing the driver's blood oxygen level.

If you agree that the most important part of the car is the driver, then you will never, regardless of the season, run for extended intervals with the Recirc on. Just because leaving Recirc on with the AC on won't cause the windows to fog up (as happens in cool/wet weather, advertising one's low[ered] IQ to surrounding drivers) doesn't make it right.

If you do not agree, then you probably need to turn off your Recirculated air.

The basis for the answer to your question lies not in mechanics or thermodynamics but in biology and caring. Big-spending penny-pinching commercial airlines demean their passengers and risk their health by subjecting them to excessively-recirculated air to reduce (heating) costs. Not-fully-alert, dulled-down cargo-passengers are a side-benefit to such corporations. Shame on anyone who voluntarily/consciously/willingly treats themselves so poorly by depriving themselves of 'fresh' air. Try to use Recirc only when the air is not 'fresh' (which will be all the time if Dubya has his way for much longer).

- Dave; '95 854T, 143K mi

With all due respect, there is a difference between a tech and a mechanical engineer (though some are both). Running A/C in a recirc mode is the most logical and efficient way to operate a cooling system. It is, in fact, less demanding on the system. Do you leave the windows open in your house in the summertime when running the A/C?! As you point out, the recirc mode reduces the condensate rate, and the air inlet path has lower pressure loss.

Common sense does need to prevail, though. When in recirc mode, the air will get more stale and will get colder and dryer (less humid) if this bothers you. The Volvo manual A/C system will actually cycle the compressor when/if the evaporator coil gets too cold. And you may want to end your trip with the A/C off and with fresh air to let the evaporator dry off (keeps the possibility of mold down and may aid in slowing corrosion of the coil).

Gerald C

I think the manual says not to leave it on REC for more than 15 minutes at a time. A reason it might be tougher on the system is that it might make some of the components too cool - like freezing it out. Mine blows cold in the fresh air position even during the summer (95-100 degrees daily). The REC helps cool it off faster sometimes, though.

I work for an independent volvo repair shop in houston and I have never heard of any problems with keeping the ac on rec. I leave mine on constantly and have had no problem. If you are worried about the evaporator you have a good reason to. The 850's are notorious for the evaps going out on them, and the repair is amazingly expensive. Replacing the evap consists of removing the dash, and you are looking at around $1100.00.