Cold Air Entering Passenger Compartment?

[Tom in Tacoma]

I'm wondering if others are experiencing this or do I have a problem in my climate control system? Here's what's happening...

With the climate control set to 'Auto' (AC is on) and the temperature is set to 73-degrees. When the engine gets up to temperature the heater starts blowing warm air into the floor position. The fan speeds up as the engine warms and continues to blow warm air. As the cabin temperature nears the set temperature the air is then blended between the floor and the dash vents.

Here's where the trouble begins...

When air is set to exit the dash vents I feel cold air coming through them regardless of how high I raise the temperature. The only way I can warm up the interior and keep it that way is to bump the temperature up to 75+, turn on the air recirculation and bump up the fan speed.

Am I wrong to expect the 'auto' setting and a comfortable temperature setting to prevent cold air from entering the cabin?

My wife particularly complains that the passenger side is cold while my right foot is melting on the driver's side.

Any ideas?

[inov8]

Have a look at this message thread and see if it is relevant to your experience.

http://townhall-talk.edmunds.com/dir...w/.f14645f/180

[Tom in Tacoma]

Thanks for posting that link but it's not related to what I'm experiencing. It's not a matter of the recirc turning off as it is the system blowing cold air from the dash vents once the inside temperature comes up to set point.

From the lack of responses it might be an issue that's unique to my car. I'll give it a few days and then take it in to the dealer (just before hitting the 36k mark!).

[osidepunker]

My car also blows warm air from the floor vents and colder air from the upper vents. I think that Toyota has decided that it would be more comfortable for colder air to be blowing out of the vents onto your face and warmer air to blow onto your feet. The ambient temperature is still 73, and since warm air rises and colder air sinks I think it works out rather well. I like it.

The issue of cold air on one side and hot on the other sounds like a malfunction.

[Tom in Tacoma]

Originally Posted by osidepunker

...The issue of cold air on one side and hot on the other sounds like a malfunction.

Or perhaps a function of the passenger?

[osidepunker]

Originally Posted by Tom in Tacoma

Or perhaps a function of the passenger?

lol you said it, not me

[Amaury]

Originally Posted by Tom in Tacoma

...With the climate control set to 'Auto' (AC is on)...

Any ideas?

The reason you’re getting cold air is simply because you’re running the AC compressor simultaneously with the heat cycle. With the compressor engaged, you’re gonna have your R-134a refrigerant running through the evaporator coils in the cabin and the result gonna be COLD AIR regardless of the ambient temperature.

Solution? Just run the heat cycle alone; there’s no need to waste any more gas by engaging the compressor. That’s what I do here in NYC every winter. And besides, running any type of AC compressor below 50 deg F is really asking for unnecessary troubles.

Amaury
'08 Limited

[osidepunker]

Originally Posted by Amaury

The reason you’re getting cold air is simply because you’re running the AC compressor simultaneously with the heat cycle. With the compressor engaged, you’re gonna have your R-134a refrigerant running through the evaporator coils in the cabin and the result gonna be COLD AIR regardless of the ambient temperature.

Solution? Just run the heat cycle alone; there’s no need to waste any more gas by engaging the compressor. That’s what I do here in NYC every winter. And besides, running any type of AC compressor below 50 deg F is really asking for unnecessary troubles.

Amaury
'08 Limited

That's not true. The system combines air from both the heater radiator and the AC. The reason AC comes on in cold weather is to control condensation in the cabin. Same reason it comes on when you use the defroster. If you don't want it on you can turn it off, but depending on the weather outside your windows might start to fog. Either way the system will still put out hot air when needed whether the AC is on or not. And the system is designed to run in AUTO 24/7 regardless of the outside temperature. In cold weather, the AC runs in an economic state and doesn't use that much more gas than normal.

[Tom in Tacoma]

Thanks for the responses and ideas guys. I'm inclined to agree with osidepunker - the AC being on doesn't necessarily mean that it will be blowing cold air. The air temperature should be regulated by the climate control setting. The AC compressor will cycle on or off depending on need to add cold air.

In my case, turning the AC off doesn't stop the cold air from entering. I'm beginning to think the cold air is a function of blending warm air with outside air. It just doesn't seem to blend very well before it exits the dash vents - hence the feeling of cold air. I suppose it's a design thing but I would think Toyota would have used an air-blending box instead of the interior cabin to mix air.

I think I'll go speak with the service adviser at the local dealer. Keep the thoughts coming!

[benalexe]

I have the same problem on my 2005 avalon. My wife always compalains that cold air is blowing. I though the reason for this is the car is just maintainng the interior temperatures and in order to not get too hot it has to blow in some cold air too.

[mickeyp]

My wife has also complained of this. I thought she was crazy. Why would it just be on the passenger side? Also, during a trip yesterday, the heat setting was on floor and windshield, yet air was blowing on me out of the dash vents. Not cold air—I think it was the set temperature.

[Amaury]

osiderpunker,

I know the AC is there to control condesation in the cabin depending on the relative humidity (RH) of the outside air, which partially controls the cabin's dew point temperature. And, Like you said, the AC is running no matter what. My whole previous comment focused on that same issue only: that the AC is running; so what part is not being true?

Condesation (fog) may or may not form in your cabin when your heater is on. I bet you that if the outside air's RH is below 60% your windows won't fog, and adding heat to an already dry air (like when you turn the heater on w/o the AC) will make the air dryer hence pushing the cabin's dew point temperature even further away so fogging wouldn't form. Don't believe me? Purchase yourself a good digital hygrometer with a dew point temperature scale and do the experiment.

And when your windows fog because of a high RH or your cabin's temperature is below dew point, then briefly use the deffoger switch (which is another way of turning the AC on). I may sound funny to some, but this is one of the critical reasonings Toyota makes when designing HVAC for their vehicles.

Do you need to run AC for the same duration as the heating cycle? You don't have to as explained above; and you end up saving on gas and the compressor useful life. Again, when the AC compressor is engaged is because somewhere there is a difference in temperature (temperature gradient), and the AC purpose is to equalize that difference or make it bigger on the cold side of the scale by producing COLD AIR; this is an established fact.

Amaury
'08 Limited
ps. I'm still interested in discussing with you what you found not true about my statement. I'll be more than happy to discuss it further outside this topic.

[Amaury]

osiderpunker,

FYI: The deffoger is what turns on the AC to reduce air humidity to the point that no condensation will occur in any surface. The DEFFROSTER, however, uses a 12-Volt, high amperage circuitry (about 15A-18A) to heat up the thin wires in the rear window to melt any accumulation of ice/snow.

Amaury
'08 Limited

[osidepunker]

Originally Posted by Amaury

I know the AC is there to control condesation in the cabin depending on the relative humidity (RH) of the outside air, which partially controls the cabin's dew point temperature. And, Like you said, the AC is running no matter what. My whole previous comment focused on that same issue only: that the AC is running; so what part is not being true?

This is the part that is not true:

Originally Posted by Amaury

The reason you’re getting cold air is simply because you’re running the AC compressor simultaneously with the heat cycle. With the compressor engaged, you’re gonna have your R-134a refrigerant running through the evaporator coils in the cabin and the result gonna be COLD AIR regardless of the ambient temperature.

I have already explained why I believe it's not true.

Originally Posted by Amaury

Condesation (fog) may or may not form in your cabin when your heater is on. I bet you that if the outside air's RH is below 60% your windows won't fog, and adding heat to an already dry air (like when you turn the heater on w/o the AC) will make the air dryer hence pushing the cabin's dew point temperature even further away so fogging wouldn't form. Don't believe me? Purchase yourself a good digital hygrometer with a dew point temperature scale and do the experiment.
And when your windows fog because of a high RH or your cabin's temperature is below dew point, then briefly use the deffoger switch (which is another way of turning the AC on). I may sound funny to some, but this is one of the critical reasonings Toyota makes when designing HVAC for their vehicles.
Do you need to run AC for the same duration as the heating cycle? You don't have to as explained above; and you end up saving on gas and the compressor useful life. Again, when the AC compressor is engaged is because somewhere there is a difference in temperature (temperature gradient), and the AC purpose is to equalize that difference or make it bigger on the cold side of the scale by producing COLD AIR; this is an established fact.

You are taking a simple subject, whether to have the AC on or off to control window fogging, and over complicating it. You do not have a proper understanding of relative humidity and I will not take the time to educate you. This thread is about why Tom has cold air coming out of the dash vents and whether that is a malfunction or not. I believe that it is running properly. As far as window fogging, I choose to run my climate control system in AUTO. You can run it however you choose. If you claim that having the AC off will save gas and extend the life of the compressor, then I will agree with you. However, I believe that the savings on gas is minimal and I challenge you to prove to me how much longer your compressor will last compared to mine. Also, don't try to lecture us on relative humidity and dew point. It is not relevant.

Originally Posted by Amaury

I'm still interested in discussing with you what you found not true about my statement. I'll be more than happy to discuss it further outside this topic

I'm not interested.

Originally Posted by Amaury

FYI: The deffoger is what turns on the AC to reduce air humidity to the point that no condensation will occur in any surface. The DEFFROSTER, however, uses a 12-Volt, high amperage circuitry (about 15A-18A) to heat up the thin wires in the rear window to melt any accumulation of ice/snow.

Are you kidding me? This is some kind of joke, right???

[Amaury]

Again, if you have an air conditioning on and a heater on, at some point you're gonna feel the cold air blowing depending on how well balance the system is.

You were the one who brought the issue about CONDENSATION.
And what I say is, condensation = fog = air mixed with water vapor = humidity. Obviously you don't know about refrigeration if say that HUMID AIR has nothing to to with RELATIVE HUMIDITY and dew point temperature.

Print out my quote and show it to someone who really knows about refrigeration; even better, see if you can find an engineer who knows about this subject and show it to him.

The 12V was a typo (makes it believed I was about DC battery when in fact I was not). The 10-20 amperes is still being fed to the thin wires.

Amaury
'08 Limited

The issue of condensation is not a simple matter. There is a whole science, actually there are two major fields, wholly dedicated at understanding it.