i've this argument with my mom and my friend but where does the a/c get its energy. what i mean is that i'd say that it draws it's power from the cars batery. but my mom and my friend says it has to do with the cars gass but i say it has nothing to do with it, but anyways what is the true answer.

I've worked on my own several cars over the years and so I say this with confidence: who knows...

No, but seriously--technically gas (fuel) is the key to everything in your car. And the battery is the kick-start to every electronics in a car. But what keeps the battery alive is the alternator. Without it, the battery will drain, the engine will not start and the car will stall. The reason car battery lasts as long as 5 years is the fact that the rate of charging is greater than discharging (head lights, dashboard lights, ipod plugs, stereo, stereo amp, heater, air conditional etc).

And the way to keep your alternator alternating (to produce much needed electricity) is to keep the engine running. To run the engine combustion is required. Gas is one of highly efficient sources of combustion.

But in the sense of "energy" to run air conditional to keep the car environment cool is Freon. The same principal was taken from your average household refrigerator. A compressor filled with Freon circulates cold temperature by means of diffusion and thermodynamics.



So the "energy" to cool the air is from Freon. But the "energy" to drive the air conditioning unit comes from electricity provided by alternator which gets its energy from engine. And the engine requires combustion to deliver, among other things, enough force to keep the alternator going.

I'd add, just to simplify Buff's explanation, that if you lift the hood of most any conventional (non hybrid) automobile you'll see a belt or several belts attached to a center flywheel and also wrapped around about three smaller flywheels attached to powered accessories. One spins the alternator. Very important to run the fan which blows cool or warm air around the inside cabin of your car. Two would be attached to the power steering hydraulic pump to make turning the wheels easier (many newer cars have electric assist here so no belt). Belt number three would be attached to the hydraulic pump that magnifies the power applied to the brakes when you step on the brake pedal. And, for cars that have A/C, belt number four is attached to the Air Conditioning compressor which is just like the one in your refrigerator except this one is powered directly by the motor and when it's cycling freon (or whatever the name of the new "green gas" is) through the condenser in front of the radiator, it draws approximately 10 - 15 horsepower from your motor costing you money in extra fuel consumed. Many newer cars also have just one belt, but it makes no difference as it's spinning all those accessories none the less. The VW Touareg and other EU VWs like the Phaeton with the optional V-10 TDI motor have a chain and gear assembly that is internal -very cool, no belts at all. But, I digress. The point is, ultimately it's the engine's spinning action that powers all your car's accessories including the air compressor. The battery may supply the juice needed to operate the fan, but it wouldn't last long without that alternator that's spinning while the motor is running. And if you shut the motor off, your cool A/C will quickly heat up because the compressor isn't spinning any more forcing Freon through the condenser thus making it cool so it can go back to the radiator inside the cabin and have the fan blow air through it making the air cool for you. Ultimately, it's powered by gas or diesel or whatever fuel is injected into your motor to make it run.

This post has been edited by Watermonkey: May 12 2008, 06:09 PM

the battery in a car is only used to give the engine that initial spin , to take throught the first cycle, to get the whole process of intake, compression, combustion, and exaust going... so the ac is not powered by the battery. once the car is running, all electricity and power comes from the engine which in turn runs on gasoline.... the battery is no longer active while the car is running, infact, the engine actually recharges the battery for a period of time after it is started.

infact, the ac is powered by the engine, and a can of compressed refridgerant under the hood in the ac compartment, which is usually located infront of the engine wall, infront of the passenger seat. this ac componet is powered by electricity provided by a rubber belt attached to the front of the engine. this takes advantage of the engines rpm and uses it to produce electricity by use of an electro magnent.... kind of like a windmill.