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Discussion Starter · #1 ·
Can anyone explain why GM made our cars so we cannot use the recirculation mode while using the defrost? When I come to a stoplight, my HVAC system sucks in the "outside odors" from the car in front of me. I also have a Honda Accord and a Honda Ridgeline and I can use the recirc button with the defrost on both of them. Is there a way to modify or program the HVAC system to allow this to happen or am I just stuck? Below is page 124 from the 2007 Sky owners manual:


(Recirculation): Press the center knob on
the control panel to recirculate air inside the
vehicle and prevent outside air from coming in.
It can be used to prevent outside odors from
entering your vehicle and cool the air inside your
vehicle more quickly. Press this button to turn
the recirculation mode on or off. An indicator light
on the button can on while the recirculation
mode is activated.
Recirculation is available in the bi-level and vent
modes. If recirculation is selected in either
floor/heat, floor/defog, or defrost mode, the
indicator light will flash three times indicating it is
not available in that mode.
 

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True for all makes for many years. Humidity from people in the car can fog the windows in recirculation mode. So they all disable it.

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Discussion Starter · #3 ·
True for all makes for many years. Humidity from people in the car can fog the windows in recirculation mode. So they all disable it.

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If it were "true for all makes for many years" "So they all disable it". It would not work in that mode with both of the Hondas I own:confused:
 

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My corvette, solstice, and xc90 require outside air in defrost but my toyota land cruiser allows to do it on inside air, it also doesn't work worth a crap at defrosting windows while on inside air but does fine on outside air.
 

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Vehicle occupants release additional moisture into the air through respiration, causing a higher humidity in the vehicle cabin than is outside. To minimize the ability of this moisture to condense on the windows, GM vehicles are forced into outside-air while in Defrost mode so that the fresh, drier air is circulated across the windows opposed to the humid air that exists in the cabin. The same holds true for any other mode that directs a significant quantity of air to the windshield. Most manufactures, GM among them, will also automatically request the Air Conditioning compressor to be on when in Defrost mode (if the outside ambient temperature is above a minimum temperature, usually around freezing). The purpose of this is to dehumidify the air as it passes through the evaporator core so that the moisture doesn't condense on the inside of the glass causing reduced visibility.

I can't explain why The Hondas an Toyotas behave differently, because it doesn't make any sense to direct moist air to the windshield. "Flash fogging" is just too big of a risk in recirc with air directed to the windshield especially on cold/cooler climates.

Everything is possible in some way, but your Dealer or repair shop will not be able to reprogram the system to allow recirculation in this situation.

Hope this explanation is helpful.
 

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Recirc on and defrost is like trying walk in opposite directions at the same time. You are making the A/C system work twice as hard to remove moisture. Better to have the outside air coming through than the recirc on as mentioned above. Your window will defrost/remove moisture much faster that way.

And yes, my AC compressor will run in the defrost mode even when it is below freezing outside.

Do you drive with the recirc button on all the time with the top up?
 

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Do you drive with the recirc button on all the time with the top up?
Better than with the top down.....:lol:
 

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isn't the cabin filter supposed to eliminate or limit outside odors? you figure it would help muffle it a little at least.
 

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The Solstice has a cabin filter?

Where?

:devil: :willy:
Its the black thing that stores in the trunk and can swing up above your head!
 

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From the Massachusetts Registry of Motor Vehicles web site Vehicle Maintenance Tips:

Check your heater, front and rear defroster for proper operation. Do not drive with the heater in recirculation mode, because there may be too much moisture from you and the melting snow on your boots for the defroster to do its job.


From Opel's manual covering automatic climate control:

Manual air recirculation mode

The manual air recirculation mode is operated with the defog button.

Warning:
The exchange of fresh air is reduced in air recirculation mode.

In operation without cooling the air humidity increases, so the windows may mist up. The quality of the passenger compartment air deteriorates, which may cause the vehicle occupants to feel drowsy.


From the 2013 Honda Pilot model information web site:

Windshield Defroster Button turns on the AC, selects air flow from the defroster vents at the base of the windshield, and switches to fresh air mode.

Sapienti sat.
 

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Discussion Starter · #15 ·
I should have stated that the only time I use the recirc button while in defrost mode (on my Honda) is when exhaust fumes or cigarette smoke enter the cabin from the car in front of me, otherwise I use the defrost as it was designed. It is easier to push a button and still have the defrost run as opposed to shutting off the defrost completely. I guess I was just curious on why some manufactureres allow you to use the recirc button in the defrost mode and some disable the fuction???
 

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I should have stated that the only time I use the recirc button while in defrost mode (on my Honda) is when exhaust fumes or cigarette smoke enter the cabin from the car in front of me, otherwise I use the defrost as it was designed. It is easier to push a button and still have the defrost run as opposed to shutting off the defrost completely. I guess I was just curious on why some manufactureres allow you to use the recirc button in the defrost mode and some disable the fuction???
If the fumes bother you, turn off the defrost until you are moving again. Honda didn't properly program their hvac. GM did. Recirculating moist cabin air then blowing it on the windshield is not smart unless you're trying to recreate the sex scene from Titanic. It turns defrost into fog mode.

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Discussion Starter · #17 ·
If the fumes bother you, turn off the defrost until you are moving again. Honda didn't properly program their hvac. GM did. Recirculating moist cabin air then blowing it on the windshield is not smart unless you're trying to recreate the sex scene from Titanic. It turns defrost into fog mode.

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It's not just Honda, its other imports like Toyota, Lexus, Nissan, Infinity, Acura, Mitsubishi, etc... There has to be a reason why "the imports" do it that way and "the domestics" do it another.
 

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Not all imports, every more recent German vehicle I've owned functions with the same HVAC logic as GM. In addition, they also use a 20 minute time-out on recirc mode to make sure that the cabin air is refreshed.
 
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