I often hear how the Air Conditioning in a car takes power away from the engine, and how it is not good to start a car with the air conditioning on at the same time. Why and how does the air take power like that, and why isn't it good to start a car with it on?

well, it's not good to start u're car with the stereo/AC/wipers/anything else that the battery world power if u're Engine is not running.. causes u're battery to work harded and gives u're engine a harder start. I have no idea what causes the AC to take so much power away.. but it does.. Usually the AC takes more power away in any automatic car.. but not as much as in a manual .:smoker2:

there are two components in the AC system that account for the majority of the power consumption:
1) the compressor
2) the fan(s)

The compressor is the big one. It can consume as much as 10hp in some vehicles. The power consumption of the AC compressor doesn't really have a thing to do with the type of transmission, size of the engine, or much else along those lines. It's related primarily to how much cooling the AC is doing.

I'd bet http://www.howstuffworks.com would have an article on the subject - try searching for "air conditioning" and see if you find anything.

Just out of curiousity, Mike, do you know what coolant current cars are using? Thanks.

Here's the best of my knowledge on that subject (off the top of my head, without any further research):

Coolant (in the radiator): water + propylene (or ethylene) glycol + lubricant additives + anti-corrosion additives

Refrigerant (in the AC): R-134a, I think...

I'm not the best guy to ask about that though.

I see. Thanks for your time. :)

R-134a is the current refrigerent in AC systems, the old kind is R-12. You can convert it over from R-12 to R-134a in oreder to be legal.

Yeah....conversion kits are really cheap too...I think they're only $30 or something like that.

The conversion kits are merely different 0-rings used to seal in the new refrigerant.

going back to what we were saying earlier...

Is the fan and the compressor hooked up directly to the engine?

Originally posted by jjguitar
going back to what we were saying earlier...

Is the fan and the compressor hooked up directly to the engine?

the compressor is driven by a either v-belt or serpentine belt.

and most cars these days use electric fans for both the condensor and blower.

if most cars use electric fans for the compressor and blower, how does that use up some horsepower?

Originally posted by jjguitar
if most cars use electric fans for the compressor and blower, how does that use up some horsepower?
Some hp is consumed by the alternator.

in fact, using electric fans means that they'll necessarily use more power when they're on than the same fan would use under the same conditions if it was mechanically driven. You lose energy when you convert from mechanical to electrical (alternator) and again when you convert from electrical to mechanical (fan motor). The nice thing about electric fans is that they can be turned off when you don't need them, which means that you end up using less power overall.

ok, I think I understand now....thanks!