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Old 06-22-2011, 04:35 PM
FireRanger FireRanger is offline
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Default Re: Air Conditioning and Gas Consumption

It would seem that way... except the compressor isn't chilling anything, and nothing in the AC system is operationally based on temperature. The compressor is just compressing to set pressures. It will make the pressure regardless of temperature.

The chill comes from two things. Air going across the condenser coil draws heat away from the compressed and heated freon (reducing its temperature some) causing it to condense into a liquid. Condensing gives up heat which is why air blowing over the condenser coil is hot. When that freon now goes into the evaporator coil inside the truck, it goes through an expansion valve too which causes it to expand (decompress...). Adiabatic cooling causes a steep drop in temperature which is where you get your cold from. It then goes back to the compressor and starts over.

So you see, an air conditioner actually has very little to do with temperature and very much to do with pressure. The temperature is merely a very useful side-effect that doesn't actually effect much.

The only time temperature and air flow can effect things is:
- A lack of air flow over the condenser will cause it not to condense. That's why it stops working if your engine fan isn't spinning while you aren't moving.

- A lack of air flow over the evaporator can cause it to ice up due to humidity. It doesn't actually stop the system from working though, as it remains a solid block of ice until you shut it off and let it thaw out.
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Last edited by FireRanger; 06-22-2011 at 04:39 PM.
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