Does the front defrost effect or control the air conditioner in any way? I have noticed that my Prius begins to lose mpg when the defrost is on (even when the temperature control is set high) as opposed to the vent/blower. I have a volvo that automatically turns on the AC when the defrost is turned on and was just wondering if this could be a similar case with the Prius.
I believe so. 60mpg doesn't do you any good if you can't see through the windshield. Just accept it or park in a garage.
With the front defrost on the engine doesn't shut off as often. In fact most times if you start the car with the front defrost still on the engine will fire almost immediately after powering on the car rather then waiting the full 7 seconds or so that it usually does.
Yes, the defrost mode uses the A/C to dry the air that is sent to the windshield. That's why it works so well and can clear the windshield in just a couple of seconds.
A few seconds? That's for a fogged windshield. You basically just defog it. Come try it here in Canada (or nothern USA) at -10F, it'll take much more than a few seconds to "defrost" (aka remove the frost - the formation of frost or ice on a surface ).
Outside the frozen tundra we refer to removing the mist on the window as defrosting because it gives the windows a frosted look. I think ice needs to be scraped off if you chose to live in colder climates. I have to deal with ice about twice a year.
FYI we scrape the ice on the outside of the windshield. The inside gets defrosted by the car's heater.
