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Discussion Starter #1
Is it possible to modify the climate control system to be able to use the defroster while recirculating inside air?
 

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It may be possible, but it would be a waste of time doing it, since you would quickly find you would never use it.

On cold days, any moisture that evaporates from the snow/water on the floor, or from your breath, will condensate on the cold windshield to form fog or frost, depending on the windows temperature.

The idea of defrost mode is to blow warm, dry air. Remember when air is heated from the freezing point to room temperature, it's relative humidity (RH) decreases. In other words the warmed air has the ability to hold more moisture than when it was cold.

This air with this lower RH dries the fog/frost from the windshield.

If you run the defroster in recirculate mode, the temperature will not rise enough to reduce the RH. In fact as it gets warmer in the vehicle and the water/snow on the floor evaporates, the RH will actually increase and cause heavier fogging of the windows.

That is another reason why the AC will turn on in the defrost mode to cause even more of a drying affect on the air.
 

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Discussion Starter #3
Thanks for the reply, Rick. I'm fully aware of your description. My wife has environmental sensitivities and needs to keep road pollution out of the car, even in defrost mode. The problem you describe above can be somewhat remediated by using the AC while defrosting in the recirculate mode. In my 2005 RAV4, I was able to push the recirculate button in on defrost mode. On the 2011, the button will not stay in. I am tempted to use a mechanical method of holding the button in.
 

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Thanks for the reply, Rick. I'm fully aware of your description. My wife has environmental sensitivities and needs to keep road pollution out of the car, even in defrost mode. The problem you describe above can be somewhat remediated by using the AC while defrosting in the recirculate mode. In my 2005 RAV4, I was able to push the recirculate button in on defrost mode. On the 2011, the button will not stay in. I am tempted to use a mechanical method of holding the button in.

I agree that the system in the '11 RAV is arbitrarily designed and eliminates options which users may need or wish to use. Three are times when I don't want the A/C to be used when I have the system in Defrost mode, for example, and the problem with Recirc not working when in Defrost mode is another annoyance. On my previous Honda CR-V the system was totally flexible and each function could be defined by the user. Toyota dropped the ball regarding this on at least the '11 RAV. I hate it when some engineer can arbitrarily determine what I can and cannot do with this sort of application.
 

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Yep, I recall that this was a topic for discussion earlier. The problem with the first and third threads is that the Techstream/dealer option works only with the automatic climate control system, not with the manual system. The middle one involves some disassembly of the dash, something which I wouldn't want to contend especially if I were to break something or cause a problem which my extended VSA would not cover. Someone also had an even more involved solution which involved disassembling the switch itself.
 

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Discussion Starter #7
Thanks to all for your suggestions. I phoned the service department at Western Slope Toyota in Grand Junction, CO. A Toyota tech there said he's pretty sure he can do some "after market engineering" to meet my needs. I sent him some of the first two links mentioned above. I'll post more when there is more.
 

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I find this to be a pointless endeavour...
#1 you rav has a cabin air filter so you should stay on top of that.
#2 outside air will still come into the rav no matter what...if it didn't your wife would run out of oxygen and die.
#3 will using the recirc function pass the air thru the cabin filter? If not then any outside contaminates will just keep getting circulated since she must open the door to get inside the rav. Opening the door will allow all kinds of things in the rav.
 

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I find this to be a pointless endeavour...
#1 you rav has a cabin air filter so you should stay on top of that.
#2 outside air will still come into the rav no matter what...if it didn't your wife would run out of oxygen and die.
#3 will using the recirc function pass the air thru the cabin filter? If not then any outside contaminates will just keep getting circulated since she must open the door to get inside the rav. Opening the door will allow all kinds of things in the rav.
I tend to agree with some of your points. I have found that when seeing a cloud of smoke up ahead(fire say), I hit the recirc button, but when I get there, I still smell the smoke anyway.
 

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Discussion Starter #10
Thanks again folks for airing your views. I know there are vents always open in the rear corners of the rav, which allow outside air in all the time. And there's a lot more coming in when not on recycle through other vents. One can sense this as the faster one goes, the stronger the air flow is. Thus, while some of what you aver, ravenuer, is certainly true, I would maintain that recycle mode does reduce the road pollution in the car.
 

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On my 2011 RAV4 Sport model, if I put the selection on the combination of heat+defroster I can put it in recirc mode. Not all the air is coming out of the defroster vents as some is coming through floor vents, but it does defrost in recirc mode this way.
 

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Even in recirculating mode, a significant amount of external air is still drawn in.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #13
Thanks Stephen and WJ. Unfortunately my recirc button pops out when mode is between straight heat at the feet and heat+defrost. Also, WJ, I know it does. I have found there is a PREMIUM cabin air filter which has a carbon coating to filter incoming air. A mechanic has said all incoming air passes through this filter. I now have one of these filters and still have experienced some exhaust smell from incoming air. Oh well! Also, with the car engine off, I have carefully listened to the sound of the flap closing when the recirc button is pushed (and released, with light staying on) in other modes. Then I pushed the recirc button and held it in defrost mode (light stayed on). The sounds were exactly the same as above in other modes. This led me to think that the electric motor closing the flap has a limit switch which is activated (i.e. the electric motor turns off) when the flap closes, even if the recirc button is manually held in. A Toyota mechanic agreed with me. So I have rigged a way to manually hold in the recirc button when needed. If anyone knows, or suspects, there may be a problem with this, please reply. FYI--The above mechanic has agreed to look at some of the earlier suggestions in this thread to decide if he feels competent to take the dash apart and do a more "conventional" fix. Thanks to all who have read this thread and replied.
 

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Unfortunately my recirc button pops out when mode is between straight heat at the feet and heat+defrost.
Why put it between the settings?

Mine works perfectly well when set to the correct detents.
 
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