Just noticed a quirk that seems weird. On all my other cars, when the recirculation buttom is pressed, the sound of the A/C changes due to the venting changing. On my FEH, pressing the recirc button does nothing I can hear... Only the light comes on. Is this the same on yours? or is mine broke? thanks

 

My 2008 increases the sound when recirculate is in effect. It sounds like you may have a problem.

 

As far as I know, with any car, when you switch from fresh air to recirculating air, the air blows a little harder.

 

We have an '08. When I switch to recirculate I notice absolutely no difference in sound....only difference is the light. I thought this was odd too.

 

I think it depends on the blower speed.

If you have the fan on Max. Speed, I think you hear a change in noise as the "turbulence" inside the box changes.

At slower fan speeds, this may go unnoticed.
That's my guess. I have a 2005.

 

In fresh mode the system is typcially quieter due to the (HIGH speed) blower air intake NOISE being outside the passenger cabin, at the outside base of the windshield. In recirculate mode the system air intake NOISE is typically inside the passenger cabin just behind the traditional glove box location. The use of good, fairly thick pollen filters has served to "quiet" the intake noise overall so you likely will not notce a difference except at the highest blower speed and/or with a rear window lowered in fresh intake airflow mode.

In order to improve FE by keeping "conditioned", previously conditioned, airflow within the passenger cabin for a longer period the exhauster port has now been reduced to restrict cabin air outflow. So these days fresh mode will not be able to move as much airflow as yesteryear.

Oh, almost forgot...

Many US manufacturers now use Denso US, a subsiderary of NipponDenso Japan, to design and produce their HVAC system components. Denso has become quite famous (infamous..??) for their flawed, sometimes HORRIBLY flawed, even deadly, poorly though out, automotive HVAC designs. Denso actually has a US patent wherein the system airflow structure/design will potentially ALWAYS (under automatic control not manageable by the driver) remain at least partially in recirculate mode, even in the DEAD of winter. The idea is to restrict the recirculated, possibly (probably..!!) HUMID, system airflow near the floor level, while the upper cabin airflow near the windows and windshield, is "sourced" from the fresh (dryer air) inlet.

Why do such an idiotic thing...??

Ask the Prius' Denso/NipponDenso HVAC designers, where engine heat carries with it an FE cost premium.

So, unbeknownst to you, you may not be switching, fully, from fresh to recirculate and vice versa.

 

I didn't notice much difference in noise or flow between vented and recirculated air settings until I added a cabin air filter to my '08 FEH. Now recirculate moves much more air and is a bit louder in the cabin (when the fan is on high). I don't mind the difference because I'd much rather have the air filtered when requesting outside air.

 

UPDATE -- placed the blower on high and I did hear a flow change. but I can't hear a change on lower speeds, so I guess it's working. Thanks for all the input