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Discussion Starter #1
Starting Conditions:

A/C = OFF
Blower Fan = OFF
Recirculation = OFF
Outside temp = 54 F

Observation:

Incomming air is significantly warmer than 54 F.

Pressing Temp UP/DOWN control on steering wheel does nothing.

Work Around:

Turn on A/C or Blower motor
Turn temp to MAX Cold
Turn [strike]on[/strike][insert]off[/insert] A/C or Blower motor

Conclusion:

Heat still being applied to incomming air, despite my desire to have the system OFF. Further, OFF cannot be used to describe the HVAC system of a Toyota Prius, as it will still try to match thermostat temperature.
 

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Remember when cars had actual vents on both sides you could open to bring in outside air? Every recent car I have owned heats the air even when the climate controls are off and only the fan is on.
 

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I had the same problem in my MINI Cooper with Auto A/C.

This is why:
1)
Auto A/C stays put at the last setting when turned off. For example, a setting of 70 degrees F usually results in the A/C compressor running part of the time, and being balanced against some heat coming through the heat exchanger. The only way coolant flow through the heat exchanger is turned off in Auto A/C mode is to set temp to Max Cold.
When deactivating Auto A/C without having heat exchange afterwards, you have to set temp to max cold first.

2) The steering wheel temp up / down controls only work in Auto A/C mode, they do not work with Auto A/C off.

However, with Auto A/C already deactivated, you can manually set the temp to max cold through the touch screen menu.

Hope this helps.
M.
 

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I don't think A/C is strictly balanced with heat, esp if cabin temp is higher or equal to desired temperature (within tolerances and adjustments for solar radiation and humidity). Remember, both fan and AC compressor are continuously variable, unlike conventional systems with fixed, one speed compressor and 3 to 5 step fan. However, if heat must be used to accomplish the desired task, it will.
 

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Fresh air?

So how does one get just fresh air to come in the car?(with the windows closed)

PS-I usually turn the A/C button off on cold days and keep the fan high and the temp at MAX. Why waste gas?!
 

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Discussion Starter #6
DanMan32 said:
I don't think A/C is strictly balanced with heat, esp if cabin temp is higher or equal to desired temperature (within tolerances and adjustments for solar radiation and humidity). Remember, both fan and AC compressor are continuously variable, unlike conventional systems with fixed, one speed compressor and 3 to 5 step fan. However, if heat must be used to accomplish the desired task, it will.
But you think OFF would mean OFF. Ignore all settings and just vent in outside air w/o alteration. Not that it will matter in two weeks when it's 90 degrees until September
 

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But that doesn't happen in a conventional car. When you have the temp slider past 'max cold', you are manually operating a valve allowing coolant flow to the heater core. It doesn't care if you have the fan/AC running or not.
 

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Discussion Starter #8
DanMan32 said:
But that doesn't happen in a conventional car. When you have the temp slider past 'max cold', you are manually operating a valve allowing coolant flow to the heater core. It doesn't care if you have the fan/AC running or not.
True, but you can operate that valve even when the ac and fan are off... in the Prius, you cannot because those controls are disabled under those circumstances.
 

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Isn't there a dealer setting (or maybe user-selectable) to have zero airflow when the system is off? That might stop the influx of heated air.

I'm not a fan of this system, but it cools nicely and in temperate SoCal has enough heat. But it's a bit clumsy to do things that would be simpler on a conventional system. I'm getting used to it, though.

As an aside, I noted the side window defogger vents at the outside edges of the dash are aimed right at the JBL front tweeters. I'm betting those speakers will dry out rapidly and have to be replaced. Too bad the little baffle can't be swiveled.
 

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KTPhil said:
Isn't there a dealer setting (or maybe user-selectable) to have zero airflow when the system is off? That might stop the influx of heated air. . .
I believe that's called "recirculate".
 

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No, I remember reading about a setting (not from the regular climate control panel) that changes this fresh air flow when off setting. Either that or I've got to change my meds...
 

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I've generally been able to control the temperature of the incoming air by checking what the car thinks is the outside temperature compared to what the interior temperature is set to, and it seems to behave sensibly (i.e the air is cool if the outside temp is higher than the selected inside temp). Also, I've been able to get the climate control panel to set to fan only for example, although you have to check to make sure you really have what you want because some selections seem to reset other selections. But the bottom line is I can control the A/C pretty much as much as I could in my old car although I have to use the touch screen to do so -- but the automatic system actually works pretty well and now that I understand how it functions, I'm rarely overriding it anyway. Am I missing something?
 
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