chrisvr6

Not sure if its better to have the a/c button on or off with the heat.

jonUF02

keep it on, or your windows will fog up inside due to humidity.

The G Man

I always leave it off, if the windows fog up, then I turn it on. I am sort of a control freak when it comes to cars. I do not like wasting gas and using up HP on the AC when it is not needed.

rediesel

I always have the AC on even during the winter to dehumidify.

I'm pretty sure G man your 550 has plenty of HP to spare and we're not really concerned about wasting gas driving blown V8s.

I do turn the whole system off if I'm seriously racing/testing out my car.

looney100

I would assume that the system is smart enough not to engage the a/c unless it's needed, so I don't think extra consumption would be an issue.

I suspect the on/off button is just enabling its activation if needed.

The G Man

In most of the newer system, it is a Clutch-Less Variable Displacement AC Compressor. There is very little drag on the powertrain when operating in low, but there is still some drag.