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I just had the A/C in my car die on me again; air coming through the vents with the A/C is just as warm with it turned on as off. However, my fridge/freezer is something I've had for over 5 years and it just keeps trooping on, cooling the food fine. I've known freezers to last fine for 20+ years.

I presume that both the car A/C and fridges/freezers operate on the same principle of refrigeration, and yet cars seem to need "re-gassing" every few years or the A/C will stop working. Why is this? Why can't they make car A/C as reliable as your fridge or freezer's refrigeration?

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2 Answers 2

up vote 14 down vote accepted

They are not even close in comparison.

Your refrigerator is a small sealed unit that averages 488 BTU, the compressor speed is controlled to operate efficiently as possible, and is designed to operate in a controlled environment.

According to electricity expert Michael Bluejay, the average refrigerator uses 488 BTUs per hour in normal use.

Read more

Your car Air Conditioning is about 5 Tons (60,000 BTU) at highway speeds. Yes sixty-THOUSAND BTU, not a typo. The compressor has to operate at a variety of speeds, from idle to redline, and a wildly wide range of thermal load, and temperature. The entire system has to put up with vibration and movement, and is assembled with lines that bolt or latch together which give many more points for failure.

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Sounds about like what I said ... but you said it so much better, so I +1'd yah. :D –  Paulster2 Jul 17 at 19:33
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Started on that when I saw the question and then 18 ADD leaps later I came back to finish it lol. Seen yours after I posted. –  Larry Jul 17 at 19:38
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You're first line could also hint at another, broader comparison. The primary purpose of a refrigerator is to keep things cool to help preserve them. The primary purpose of a vehicle is transportation, which may or may not include the comfort of potential passengers as a secondary concern. Hence, the design hurdles necessary for an AC unit in a car. –  Ellesedil Jul 17 at 19:49
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@MarcStober to some extent yes, with a constant and predictable power input the compressor can be designed to turn at the exact RPM required for maximum efficiency –  Larry Jul 18 at 4:52
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@jnovacho I think "tons" here is a measurement of cooling power that is not really related to weight, according to this article it has something to do with the power needed to make a ton of ice: energyvanguard.com/blog-building-science-HERS-BPI/bid/55629/… –  Marc Stober Jul 18 at 12:12

It has to do with the type of compressor which is used. The system in a refrigerator/freezer has a completely closed unit, where the compressor is housed inside of the gas. Because of this, all the lines associated with it can be soldered shut with hard lines, etc. Because of this, a house refer/freezer will not cool as quickly, either. They work very well, but you also have insulation and a lot smaller volume to cool.

A car's compressor is housed outside and the refrigerant pumps through it, with lines which are made of rubber, and seals which deteriorate over time. As long as the seals and hoses remain in good stead, the car's A/C usually will continue running without issue. Lot's of times it's lack of use which causes A/C equipment to go bad. Vehicle A/C units cool a relatively large volume of air (as well as everything in it -- such as seats, dash, glass, etc.) in a very short time.

We expect much more out of a car's A/C than we do out of a refrigerator. They don't stand up as well because it is made to work and work fast, which has the effect of wearing out faster. If you don't want the car to cool as fast, I'm sure they can make one which will last longer.

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