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Old 06-22-2002, 12:53 AM
MaxTheVool MaxTheVool is offline
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engine coolant vs. refrigerant

this came up in a debate with a friend:

are auto engine coolant and auto air conditioner refrigerant the same thing?

Specifically (if it depends on make/model), are they the same thing in a Saturn sedan?


And can someone provide a link to an authoritative page that explains this, if one exists? (I googled around and could not come up with anything definitive)



thanks
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  #2  
Old 06-22-2002, 01:18 AM
Doc Nickel Doc Nickel is offline
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They are most assuredly two seperate working fluids in two entirely seperate systems.

The engine coolant is merely a water/glycol mix circulated through the "water jacket", or passages in the engine block. It works at relatively low pressures (around 15 psi and under) and requires nothing more interesting than a simple impeller pump driven by the accessory belts.

The A/C coolant, on the other hand, requires a "cryogenic" fluid- something with a fairly low boiling point. It's cycled through a more complex system of pressurized evaporators and specialized pumps.

Yes, it can be said that both use a working fluid to take heat from one point and discharge it at another, but they are definitely not one and the same. An A/C equipped vehicle will have two "radiators" in front, one for the engine coolant and one for the AC coolant.

I don't know of a specific reference, but you might try http://www.howstuffworks.com/
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Old 06-22-2002, 01:36 AM
sailor sailor is offline
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The engine is cooled by water to which some antifreeze is added (for obvious reasons). The air conditioner works on a totally different principle. It uses a refrigerant like freon or r-134 which changes state from liquid to gas along the cycle. The compressor compresses the gas to a high pressure, which elevates the temperature. This gas goes through the condenser radiator where it releases heat and changes state to liquid form. The liquid then goes to the low pressure evaporator where it evaporates and absorbs heat. From there back to the compressor. This is called a heat pump and it is the same as your refrigerator or air conditioner. If you puncture the circuit the refrigerant will be lost in the form of gas and you need to take the device in to be repaired and recharged.
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Old 06-22-2002, 06:34 AM
kanicbird kanicbird is offline
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Can I convert a car a/c to R-12 (the good stuff)

Not that I was going to but I just wanted to know since r-12 blows all other car freons away. It seems that R-12 to R-134a kits are available so you just basically have to add the newer freon and your set to go.

What if I had a car with R-134a and the a/c wasn't so great, could I easily convert it to R-12 to get some extra cooling?
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Old 06-22-2002, 06:41 AM
kanicbird kanicbird is offline
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[b] Ignore that above - it was ment to be a new thread:
http://boards.straightdope.com/sdmb/...hreadid=121843

Turn off that 60 second time limit!!!
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  #6  
Old 06-23-2002, 04:57 PM
Gary T Gary T is offline
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Air conditioning systems keep people cool in hot weather, so it's logical for laymen to assume that the fluid used in those systems is called coolant. Logical, but wrong. It's a matter of definition, and there is no debate about it in the auto repair field, nor is there any difference among various car manufacturers.

Coolant, which in autos is always engine coolant (as opposed to say, nuclear reactor coolant), keeps the engine from melting. Another way to say it is it keeps the engine (relatively) cool, so it doesn't overheat.

My understanding is that in all types of air conditioning and refrigeration systems--home, auto, restaurant, food transport, etc.--the fluid in the system is called refrigerant. That's what the "R" stands for in R-12 and R-134a (used in cars), R-22 (used in some home units), etc.

I don't have a cite, but you can ask any auto repair professional and you will get the same answer. You can also read the labels on antifreeze and refrigeration products.
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  #7  
Old 06-24-2002, 01:46 PM
MaxTheVool MaxTheVool is offline
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Thanks to all who replied.
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