Defrost with air recirculation ON

[shafiro]

Air recirculation "can be engaged manually in any airflow mode except defrost".
So in winter traffic jam, defrosting is bundled with inhaling flue gas from the cars in front.
Since defrosting can work with recirculated air to some point, Is there a way to hack this?

 

[ProjectSHO89]

Use the bi-level (floor/defrost) setting. It allows recirc to be controlled manually.

HVAC logic disables the recirc control and only allows fresh air in when the control is set to DEFROST. You'd have the truly "hack" the system (manual wiring/controls) to override the factory (il)logic.

 

[peterk9]

Air recirculation "can be engaged manually in any airflow mode except defrost".
So in winter traffic jam, defrosting is bundled with inhaling flue gas from the cars in front.
Since defrosting can work with recirculated air to some point, Is there a way to hack this?

Welcome to the Forum.
I don't believe anyone has ever commented on this. Keep in mind that even with 'recirc' OFF, the cabin is not air-tight. I seldom get caught up in bumper-to-bumper traffic, but have on occasion noticed some fumes from other cares even with recirculation OFF.

Peter

 

[ProjectSHO89]

You might have it backwards.

With RECIRC set to ON, the air inlet door is closed and cabin air is recirculated. With the mode set to AUTO, the HVAC module decides when to open or close the inlet door. RECIRC is a user-selected option for all other operating modes EXCEPT DEFROST.

 

[shafiro]

Use the bi-level (floor/defrost) setting. It allows recirc to be controlled manually.

The most valuable tip. Thank you!

You'd have the truly "hack" the system (manual wiring/controls) to override the factory (il)logic.

So far I have not been able find any online documentation of this magic.

Welcome to the Forum.
Keep in mind that even with 'recirc' OFF, the cabin is not air-tight.

Thank you
Yes I am aware of that, however this is "not air tight" vs "wide open"...

 

[MattMPA]

Using recirculate is more likely to allow windows to fog up in more damp weather.

 

[ProjectSHO89]

So far I have not been able find any online documentation of this magic.

I haven't written it yet... Kinda just hatching the idea.

Using recirculate is more likely to allow windows to fog up in more damp weather.

Nope. The operating A/C system will pull the moisture out of the air either way.

 

[Odrapnew]

Nope. The operating A/C system will pull the moisture out of the air either way.

Technically, MattMPA isn't wrong.
It is true that running recirculation will hold on to more moisture inside the vehicle, regardless of A/C status.

Yes, the A/C should dehumidify the air, however, A/C doesn't run in cold temps (something like 40F and below), so it could below that temp and humid. Or if you track snow inside and it melts, interior humidity goes up and can cause the windows to fog on the inside.