AC button

Rhino,

I would leave it off. The only time I would think it makes good sense, is when calling for "Cooling", so in essence in the warm weather you can use AUTO and HIT A/C. It will maintain the cabin temp as you have set in degrees.

If you have the cool winter months and such, I would leave the A/C button off at that time.

So far that is what I have been doing and it works well that way. This is my usage and opinion though...

 

Which year Prius are we discussing?

 

The whole reason that the buttons have LEDs is that they are momentary switches (pushing simply completes a circuit which passes an input to a computer) and the actual change of function is carried out by the computer itself. As such, the A/C controller can decide to modify any settings.

The fact that the A/C button's light is lit up does not necessarily mean that the compressor is running. The car can vary the speed of the compressor and turn it off completely depending on the demand for cooling or drying the air. If the humidity is fairly low it won't run the compressor at all, or will cycle it.

If it is the same as Gen 2 - which is unclear - the Auto mode, if enabled, will vary all of the other settings to maintain temperature and relative humidity. On my car, pressing Auto automatically enables A/C. If this mode is active, you can press the A/C button to force the compressor off - it will continue to vary the fan speed and outlets. Gen 3 is an improvement over Gen 2 in that at least this is a physical button, rather than being a 'soft' button on the touch-screen.

I believe it was actually a configurable option whether pressing AUTO automatically enabled A/C; this isn't listed in the 2010 US Owner's Manual but it could still be an option.

 

Rhino,

My experience in my '10 has been that, even in full AUTO mode, the A/C button does enable or inhibit compressor operation. As others have said, the climate controller will regulate compressor operation and output to match need. However, with the LED off on the A/C switch, it will not use the compressor at all.

At least where I live, there is a compelling reason to leave it lit, even if cooling isn't required -- dehumidification. Those damp 45-50°F days will leave you with quite heavily fogged interior windows without the compressor supplying dehumidification.

(On a tangential topic -- does anyone know the low-temp cutout of the compressor? Is it approximately 40°F OAT as with more "conventional" vehicles?)

 

Chris,

According to page 277 in the owners manual it clearly states:

A/C Mode will not operate by pushing the Auto button.

I am going to reiterate that if you want the compressor to run then you will also need to hit the A/C button.

Auto will control fan speeds and temp in the vehicle based upon what's set. If you need additional cooling, you will need to hit the A/C button until it is lit.

Hope that helps!

 

Bob,

That's pretty much what I said -- that the A/C button works independently of the AUTO button: