An optional air conditioning mode for your car's control panel. When this mode is set, your air conditioner comes on when your brake pedal is pressed, and is switched off when the brake pedal is released.

The idea is to use your AC *only* in situations where you are braking, thus focusing the inefficiency of AC with the necessity for braking.
-- napoleonbag, Jul 23 2008

I do this manually. Not all the time, but sometimes. Downhill gradients are fair game as well.
-- Texticle, Jul 23 2008


Existing A/C systems don't appreciate being pulsed on and off like this, but with a bit of redesign that could probably be overcome; maybe some sort of pressure accumulator would do it. [+]
-- 8th of 7, Jul 23 2008


I do this manually too at stop lights, etc. [8th of 7], do you think doing this will shorten the life of my AC, or damage it in some way?
-- napoleonbag, Jul 23 2008


I don't understand what "focusing the inefficiency of AC with the necessity for braking" means. This may be a language problem. To me, you can focus on something, or perhaps focus a telescope, but how do you focus an inefficiency?

Is there something technical to braking that makes it cheaper to run the AC? Is there some reason that people who are braking need the AC more than people who don't?
-- jutta, Jul 23 2008


It's possibly? cheaper in brake pad replacement costs (due to increasing time between replacements) in an automatic by sapping the power of the engine with the AC use.

I often depress the clutch & coast for a while before braking in standards, though.
-- Zimmy, Jul 23 2008


//I often depress the clutch & coast for a while before breaking //
sp. "braking" (I hope)
But then you consume fuel running the engine.
A modern car will cut the fuel when the wheels are running faster than the engine, so coasting is a waste of fuel.
-- AbsintheWithoutLeave, Jul 23 2008


Ha! (I must have been thinking back about one of my first cars. They broke all the time).

AWL, I did not know that that was a feature of the fuel injection system. I feel kind of dumb for doing that now.
-- Zimmy, Jul 23 2008


[jutta], air conditioning puts added strain on the engine, reducing fuel economy. The idea is to therefor only use AC when a reduction in fuel economy is inevitable, just as hybrid cars use the braking mechanism to generate electricity which is then stored in batteries for later use.

If you've ever driven a small (auto transmission) car, and switched on the AC while driving, you can sense the tangible pull on your engine.

Using your AC as a brake is not intended to reduce wear on your brakes, as I doubt any benefits would be measurable. The benefit would be the luxury of occasional & intermittent AC without the guilt of lower fuel economy.

Of course, if you are such an economical driver that you coast to a stop and never use your brake pads, then this is not for you.

Another note: I posted this in regards to an automatic transmission vehicle. I suspect a manual transmission version would be more elaborate, as MT drivers don't always just hit the brake pedal to slow down.
-- napoleonbag, Jul 23 2008


I've always wanted a switch that kills the AC whenever the clutch is depressed. I hate forgetting the AC is on and coming off the clutch from a stop- in my poor little 113hp car, it makes all the difference.
-- ericscottf, Jul 25 2008



random, halfbakery