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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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  • Try operating your fridge on a moving platform and you´ll see! BTW: Car aircons should get a yearly service (refill and disinfection) don´t drive it until it´s empty, you can hurt your compressor unit! – Daniel Jun 22 '18 at 8:17
  • Unless you have a leak (in that case, refilling a system with a known leak is against the Law), there's no need to do it yearly. Once every 3 years might be enough, provided you let the compressor run for some minutes every week so that the shaft seal and o-rings stay lubricated and the natural leaking is greatly reduced. Yes, low refrigerant charge can kill the compressor because the refrigerant moves the oil across the system so that the compressor parts might find themselves with no lubrication if the pumping action pushes the oil across the system and nothing returns from the suction port. – Al_ Jun 22 '18 at 10:23
  • @Daniel On the other hand, i've witnessed the result of no AC service whatsoever and turning AC on only in the Summer, in 8 years and on an internally controlled variable displacement compressors (these have no low pressure switch so they won't sense the low charge and cycle; they actually destroke earlier in that case). One day, the thermal fuse on the clutch coil popped (due to compressor overheat) and the compressor stopped engaging. After receiving a new coil and a regas, the same compressor is still doing its job nicely after 15 years. I'm now treating that AC system much better, however. – Al_ Jun 22 '18 at 10:29
  • The thermal fuse cuts off at a 187°C temperature and is supposed to sense the clutch plate slipping against the pulley (due to the internals starting to bind because of insufficient lubrication, for examples) or getting too hot for whatever reason. Wonder if i would have had a seized compressor if there wasn't no thermal fuse at all, but, anyway, the compressor is still icing things up with no abnormal noise at all (except the normal pumping noise any compressor makes)... – Al_ Jun 22 '18 at 10:40
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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 – Pᴀᴜʟsᴛᴇʀ2♦ Jul 17 '14 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. – Move More Comments Link To Top Jul 17 '14 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 '14 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 – Move More Comments Link To Top Jul 18 '14 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 '14 at 12:12
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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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  • As a quick (and probably over-simplified) summary: a refrigerator has one moving part. A car AC has far more. – Mark Jul 8 '16 at 1:51
  • Yup. Shaft seals. It's almost always the shaft seals that go. – Nick Sep 6 '16 at 13:29
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Fridge is not a good comparison, it's much smaller than any AC unit. But that's irrelevant, house AC is larger than car AC, yet still delivers fridge-like reliability.

Both house AC and a fridge compressors are driven by electric motors. They are sealed inside one housing with the compressor with only electric contacts sticking out. This means they are perfectly sealed and coolant cannot leak.

Car AC compressor on the other hand, is driven mechanically by the engine. This means there is a rotating shaft that must enter the compressor housing. There is a seal on this shaft, but it's a moving joint, so it can't be perfect. This is pretty much the only difference between car and a fridge. Due to it, car AC constantly leaks coolant and it has to be refilled every few years, while a fridge sits there for decades with no coolant loss.

And yes, they can make car AC as reliable as house AC. It just has be an electric-driven AC. So in cars that are either fully electric or have a generator big enough (about 5 times larger than usual!), the AC is just as reliable as a fridge. But in a gas-fueled car it's less fuel efficient, as you have to first convert mechanical energy to electricity and then back again to drive the compressor, imparting conversion loses both times. It simply doesn't pay off, it's cheaper to just have it refilled every few years.

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    Making it electric driven would also move it away from the rattly engine and put it on the firewall or inside the passenger compartment. You wouldn't lose much efficiency on the electric drive, but you would add a lot of weight to drag around. – Harper - Reinstate Monica Sep 23 '17 at 9:54
  • @Harper Electric motors are about 90% efficient, so 2 conversions end up with 81%. 19% loses is IMHO quite a lot, and it'll show on MPG. Now, everybody looks at MPG but nobody looks at "AC refill rate". So it's a negative feature in terms of car sales. You're right about the weight, would probably add smth in range of 30kg. – Agent_L Sep 25 '17 at 9:35
  • 10% is an armwave, I can assure you motors are much more efficient than that. You can tell, because that 10% heat would have to be removed from the motor, and as you can see on any motor or transformer, nothing like that exists. – Harper - Reinstate Monica Sep 25 '17 at 13:03
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    A fridge typically has to sit still for 24 hours after moving, before you plug it back in. Old fridges often die during/after transportation - So I´d argue that ny moving system can be as reliable as a fixed installation, at least not without much more effort. – Daniel Jun 22 '18 at 8:22
  • @Daniel Yeah, my point about the moving seal was that no matter how much effort you put in, it will still keep leaking coolant. We have Teslas now, so it'd be interesting to read how Tesla AC deteriorates or not. – Agent_L Jun 22 '18 at 9:33
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Air conditioning cooling is calculated on the volume of air that needs cooling-A car interior is roughly about the size of an apartment bathroom . Most cars are about 1ton (12000Btu). SUV can range upwards of 20000 to 40000 Btu (1.5-3.0 ton). If you were have a 5 ton unit in your vehicle as one person claimed..passengers would have frostbite or be extremely cold as they scraped the frost of the inside of the vehicle. A 5 ton compressor would be used in heat pump applications where the area to be cooled is the size of a 2 story house. Automotive compressors don't run continuously like they did in the old days. As a matter of fact in cars they cycle on and off depending on the system pressure. They even cycle on/off even in the winter to keep the system pressurized, lubricated and sealed.In the old days compressors wouldn't be operated in winter and a result the refrigerant would pool at the lowest point in the system the condenser coils, the seals would dry out and admit water vapor into system. As water vapor entered the system it would react with the refrigerant turning it acidic destroying the system as a result.

The basic differences between refrigerators and air conditioning is duty cycle, type of compressors used, as well as refrigerant used.

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  • Is that apartment bathroom built like an air traffic control tower, with a huge greenhouse sucking up solar load while the sun bakes the roof? That's the problem with a car. Never seen an apartment bathroom get to 160F. – Harper - Reinstate Monica Sep 23 '17 at 9:48
  • Would not make much of a difference. A 1 ton compressor is more than adequate for the interior of a car. – Old_Fossil Sep 24 '17 at 7:07
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I'm not entirely sure I understand your question. The A/C on my 1997 Golf has just failed and needs re-gassing. This will be the first time it's needed re-gassing in the life of the vehicle; 19 years old in two months.

Putting aside personal experience. Consider strapping a fridge to the bonnet of your car. Drive it for say 60,000 miles (that's around 5 years ish?), subject it to speed bumps, cobbled streets, cornering forces, braking and the general vibration of the car, not to mention the temperature differences it will experience being outside during summer and winter. Now check the operation of that fridge. I am willing to bet it will need expert attention.

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I definitely don't agree with all that has been said here. My 3rd generation Toyota 4runner air conditioning last 15 years before needing service. As with a lot of things, reliability seems to be suffering.

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  • Welcome to the site.. unfortunately this doesn't really answer the question and would be more appropriate as a comment. Once you have sufficient reputation you'll be able to comment on other user's posts. – motosubatsu Feb 8 at 11:10

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