Last post on Jan 31, 2010 at 10:51 AM
You are in the Toyota Sienna
What is this discussion about?
Toyota Sienna, Heating / Cooling, Van
#6 of 10 Re: 2005 Sienna ventilation never off [emkay]
Jan 28, 2010 (12:25 pm)
In recirculate mode there is very little cabin air "outflow" and so the cabin humidity will continually rise as a result of human metabolism, breathing, perspiration, etc, the more bodies the higher the Rh will climb.
Cool or cold climate = cool or cold interior windshield surfaces = fogging.
Regretably this all relates to dewpoint and mother nature is mostly in charge of that parameter. So it's a good idea to NEVER use recirculate when the primary HVAC mode is for heating, keeping the passenger cabin warmed.
The new 2010 RX350's automatic climate control will not only prevent you from using recirculate "improperly" but will automatically switch the system into combined floor/windshield air outflow depending on outside climatic conditions. That will tend to keep the interior surface of the windshield warmed above dewpoint even with COLD airflow impinging on the exterior surface.
#7 of 10 Re: 2005 Sienna ventilation never off [wwest]
Jan 29, 2010 (10:06 am)
Well, obviously, you haven't driven any recent American cars then. My ex-boss' Dodge Intrepid and Stratus both would shutoff the outside air damper when the fan was off. Both had manual systems.
#8 of 10 Re: 2005 Sienna ventilation never off [typesix]
Jan 31, 2010 (9:02 am)
Sorry, that just isn't believable these days when as a safety measure systems will not remain in recirculate mode with the A/C off.
A manual HVAC that has a servomotor that automatically closes the fresh air inflow path when the blower is turned off.
"Does NOT compute..!!""
"..would shutoff the outside air damper.."
The MANUAL system outside air damper, typically, has two positions, FRESH and RECIRCULATE. It might automatically move from recirculate to fresh if the blower is turned off, and more likely so, MUCH more likely so if the A/C is turned off. But it would be patently UNSAFE for it to completely close off the incoming fresh air flow.
#9 of 10 Re: 2005 Sienna ventilation never off [wwest]
Jan 31, 2010 (10:40 am)
Yes, meant to say damper goes to recirc when fan is off, rest remains, believe what you want to believe, as always. Cars are not airtight as most people think.
#10 of 10 Re: 2005 Sienna ventilation never off [typesix]
Jan 31, 2010 (10:51 am)
".. damper goes to recirc.."
I would more readily believe "..damper goes to fresh..".
Cars do not need to be very airtight for rising cabin humidity to be a problem during coolish or cold climate(***) operations. So the default damper position should ALWAYS be FRESH.
*** Climatic periods, basically, when the only usefulness for the A/C is for dehumification.