aaronazevedo

I am fortunate enough to live in beautiful San Diego, CA. Some days it is so nice, I'd rather have nice cool outside air than stale A/C air. I can shut the compressor off with the 'econ' switch, but for the life of me, I can't get fresh cool outside air to flow through the fresh air vents.

I searched, and found some folks with the same issue as I currently have. However, those posts were years old. Did anyone every solve this issue? I have the same issue and do not think it is residual heat in the dash or engine bay for that matter. I wonder if there is a fresh air flap that is broken.

This morning it was 66 degrees outside. If i put both temperatures at 64, I still got warm air from the fresh air vents with 'econ' set. So I then blasted the a/c to eliminate all residual air form the hvac system. Push 'econ', and the system went back to blowing warm air, not cool outside air.

Help?

jumper5836

Do you have the recycle button on? There are three settings. One with a recycle symbol with a "A" in the center and one with out. Having these on will prevent outside air from getting in with exception on the one with the A in the center. I think that is for it to Automatically switch back and forth. Turning it off completely open the vents for outside air to be sent in.

I believe the REST button circulates air when the car is off and it controls the fan to cycle air into the cabin. This air is heated by residual heat from the engine.
I believe that this same fresh air has to pass through the same passage way so if your engine is hot then your going to always have warm air. I don't think there is a direct vent from outside to inside. You always got your windows.

mudman2

The Cayenne AC system only really likes to be on. I don't know a way to get ambient air into the car while running.

aaronazevedo

Thanks. I've had this feature on past BMW and Porsche cars. I typically keep it off. I'm kind of a fresh air nut. My wife is the A/C hound. Given other responses to my post, it looks like I'm going to be out of luck.

Very disappointing from a car otherwise so well engineered.

mudman2

Do you have the Econ button, try it

aaronazevedo

Thanks. That has always worked for me in other cars. From my past cars, 'econ' shuts down the a/c compress and the system should still run in auto mode, albeit with no a/c. Not so in my Cayenne. Warm air only from the fresh air vents.

HD2pct

I would guess that it is operating the way you would expect - it is just not doing any cooling (removal of heat). But it's pulling air at the ambient temperature near the surface (which is different than what it says on the thermometer on the bank building, especially on a sunny, still day), and then some heat is being added as it passes through the HVAC system on the vehicle simply because that system generates some nominal amount of heat.

Unless you remove heat via the A/C, it is going to seem warmer than you might expect.

Andy E.

I'm not quite sure where the fresh air source is under the hood however, from experience I can tell you that the fresh air system does work and it works very well.

As I share the same love for fresh outdoor air when the outdoor ambient is cooler, I also use the 'ECON' button and lower the temp to 'LO'. I then immediately lower the fan speed as it automatically defaults to high speed whenever the temperature setpoint is much lower than the cabin temperature.

As jumper 5836 pointed out, both recirc buttons (if so equipped) must be non-illuminated. The system definitely picks up heat either from the engine compartment or from under the bonnet of my all-black Cayenne. However, once you reach highway cruising speeds, the air is replenished and the temperature will actually drop to within a few degrees of the outdoor ambient temperature. Within the city, it's pointless.

Andy E.

I may have accidentally found the reason why Aaron has experienced problems as the exact same thing happened to me this morning.

Temps outside today hovered around 68°F. Here's what I did to get "free cooling"; contrary to the procedure I normally follow:
1) Lower faceplate and press 'ECON" button
2) Lowered the temperature to 'LO'
3) Lowered the fan speed to three bars
After doing this, the air was much warmer than 68°F and the I had just started the car which means zero residual engine heat.

What I normally do is lower the temperature to 'LO' prior to pressing the 'ECON' button. Having said that, I then pressed the 'AUTO' button to default back to the system's original settings and then followed my normal procedure. It worked well this time.

Reason for this? Without verifying the system's design sequence of operation thru a shop manual, I suspect that the mixing flap (mixture of air through and around the heat exchanger) remains somewhat open slightly and enough to heat the cabin. If you follow the above procedure, this will not happen.

timwu12

i know this is a super old post, but I've been experiencing this phenomenon for a while now as well.

I turn the AC off by pressing the Econ button so that it draws in the outside ambient air, yet all that comes through the vent is heat. With the AC on, the vents all blow cold air, so I'm inclined to believe that the mixing valve is working properly, but does anyone else have any other fixes or explanations for why this is happening?

mudman2

The air conditioning is always on, the ECON button does not turn it off

Do you have the manual ?

timwu12

Hey Mike,

Yes I do have the manual and it states that the in ECON mode, the AC compressor is switched off and this deactivates the cooling function (e.g. to save fuel)

wrinkledpants

Yes it does. The Econ button specifically shuts off the AC compressor. That's almost exactly how it's worded in the manual.

The air coming out of the vents will always be warmer than ambient, simply because the heater core is quite large, and it's still emitting a ton of heat given it's 190 degrees. That heat has to go somewhere, and often that's into the air stream, or heating the surrounding plastics in the housing. When you shut the heat off, that doesn't mean coolant stops flowing through the heater core.

Using econ and putting the temp sensors in Low is the best you can do. That will shut off the ac compressor (100% of air volume still flows through the evaporator, though), and the temp flaps go to their closed position.

Between the engine heat coming out of the upper cowl and the heater core keeping the HVAC box nice and toasty, you're never going to be able to get 100% ambient temperature air inside the car without opening your windows or driving at interstate speeds.

timwu12

that makes sense, and that's what I figured, I was hoping there was some magical trick in case anyone thought up of one!

mudman2

Dealer tech told me once that the design isn't something that can result in natural cooling only heating. I would love fresh air sometimes but its never in a mode where that can happen, so technically its always on but without the compressor that's all, no diverter flap