Even if my home has no integrated air conditioner, I can add one in my room by buying a mobile air conditioner. But if my car does not have any air conditioner, can I create cool air with an equivalent device, like in a cigarette lighter?

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    the closest you can get is aircondition for campers,but to call them mobile might be to take it a bit too far. Commented Feb 24, 2020 at 7:54
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    Isn't any A/C unit in a car a mobile one (at least until the car hits the scrap yard)?
    – houninym
    Commented Feb 25, 2020 at 15:18

12 Answers 12


Can't believe no one has posted this yet, but:

A car in Florida which has a window air conditioning unit mounted in the rear driver side window being powered by a gas generator ratchet-strapped to the rooftop.

Source: https://geekologie.com/2019/07/meanwhile-in-florida-a-car-with-a-window.php

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    And you lost your cart because the next TÜV-engineer files a case. Either take off the illegal add-ons or loose your car
    – eagle275
    Commented Feb 25, 2020 at 8:47
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    @eagle275 laughs in "Florida"
    – MonkeyZeus
    Commented Feb 25, 2020 at 12:37
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    @eagle275 If you make it to the next TÜV with this abdomination, the police has failed to do it's job
    – Christian
    Commented Feb 25, 2020 at 17:34
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    TÜV means what?
    – WGroleau
    Commented Feb 25, 2020 at 18:21
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    TUV: en.wikipedia.org/wiki/Technischer_%C3%9Cberwachungsverein
    – davidbak
    Commented Feb 26, 2020 at 4:07

Practically no. An air conditioner is a heat pump: it takes heat from one location and pumps it to another location where it can be radiated. This takes a fair amount of power: a 12 volt auxiliary source isn't going to be enough to make a real difference. Also, the heat has to be pumped somewhere; you'd need a radiator somewhere outside of the cabin, or a heat exhaust pipe of some kind.

If you did have a portable device, the only way you could make it work without cutting a hole in your car somewhere would be to open a window in your car to let the heat out, which defeats the purpose.

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    Then mobile air conditioners in rooms wouldn't exist. They do exist. I assume they have an exhaust pipe for hot air to go outside. Commented Feb 24, 2020 at 10:54
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    @user253751 house windows have a consistent rectangular shape which allows for fitting the hot air exhaust in a relatively air tightish fashion. Modern cars have enough variation in pillar angles and curvature that you'd need a custom fitted part to accomplish the same thing. Commented Feb 24, 2020 at 12:15
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    @user253751 a cigarette lighter socket can deliver around 120W, and the mobile air air conditioners I can see draw over 1kW. You could scale that down a little for your greenhouse on wheels, but you'd still need the entire output of the alternator, several hundred watts . I looked into driving a motorhome a/c off an inverter while driving, but apart from cooling the wrong part of the vehicle the current drawn would be too much for sustained use - and I could have fitted whatever in- and outlets I wanted as I was cutting holes anyway
    – Chris H
    Commented Feb 24, 2020 at 13:41
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    I've installed one of those portable room units in a sprinter van before. My alternator is standard issue for the model and my inverter is a 2500w pure sine. You vent it through the window and then SEAL around the window, you don't just leave it open. I never had any issue's running the unit. I did need to do a little custom work to make it air tight but no modifications to the truck and it nothing hard to do. I ended up taking the unit out tho sine I was constantly entering/exiting my rear doors the unit couldn't really keep up with cooling in my case. If the van stayed shut it worked good.
    – narkeleptk
    Commented Feb 24, 2020 at 15:16
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    @narkeleptk the question is about mobile airconditioners made for cars,to use one made for use at home one needs to drill a hole in the car or find an other arangement to get rid of the heat and use a power inverter.it will work no doubt about it but it sounds like a lot of work for keping cool in the summer. Commented Feb 24, 2020 at 15:31

Back in the 1940's and 1950's there used to be a product called a "Swamp Cooler". This was effectively an evaporative cooler that you sandwiched into your partially open car window. As you drove, air flowed through the device, was cooled by evaporation and ducted into the cabin (across the top of the drivers head).

I have no idea how well these work but there is a market in vintage units plus a number of guides online showing how to manufacture a modern reproduction unit.

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    It'd probably work fairly well in the desert but not at all in a humid region. Commented Feb 25, 2020 at 16:57
  • I'm not sure why it wouldn't work in humid areas as heat transfer to water is not affected by relative humidity Commented Feb 25, 2020 at 17:06
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    Evaporative coolers work because evaporation is an endothermic reaction meaning that when the liquid turns to gas, it absorbs heat. Water can't evaporate as quickly into a humid environment as it can dry air. Sure, you can transfer heat from air to water but that's only a tiny portion of the cooling benefit of a Swamp Cooler. It's why Floridians don't know what a Swamp Cooler is but Arizonans do. Commented Feb 25, 2020 at 17:28
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    @SteveMatthews Basically, you need somewhere for all the moist air to go or else you're not going to be able to evaporate more water into the air at some point. In a dry environment, it's pretty straightforward to dump the moist air into the dry environment, while still having plenty of dry air left to use to keep evaporating water at a good enough rate for significant cooling. Basically the moisture can only temporarily store heat, unless you can physically remove the moist air from the space you are cooling.
    – JMac
    Commented Feb 25, 2020 at 17:32
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    As a bonus, it makes your car look like it has a jet engine!
    – JAB
    Commented Feb 26, 2020 at 23:05

The air conditioner in a car draws several kW of power. A cigarette lighter socket is limited to ~150 W, which is far too little to noticeably reduce the temperature in the car.

Things you can do to reduce the temperature in the car:

  • paint the roof white

And things you can do while the car is parked to reduce the temperature when you get in:

  • park the car in the shade
  • when you can't park in the shade, place an insulation blanket on the sun-facing windows

I have used home made ac units that consists of a cooler, fan & ice (see video). It works GREAT for a hour or so depending on how hot the day is. You could get a 12V DC fan that plugs into your cig lighter and set cooler in passenger floor or seat. I used to freeze a few 1.5 gallon (5.7 litre) square jugs to rotate in and out so I always had ice available and no water to dump out.


home made ac

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    Back in the late 60's or early 70's, there was actually a commercial version of a device like this. My uncle gave my dad one to put in his Ford pickup. The unit was an insulated plastic box roughly 18" wide x 15" deep x 8" high (those dimensions are childhood memories almost 50 years old, so take with a grain of salt) with legs that would allow it to sit over the transmission hump in the cab. You would fill the ice reservoir up, plug it into the cig lighter, and then it had an electric motor to circulate air over the ice and out thru some nice grills. Unfortunately, it did not work well. Commented Feb 26, 2020 at 15:33
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    This appears to be the unit my dad had: worthpoint.com/worthopedia/… Commented Feb 26, 2020 at 15:53
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    This can be called a phase-change batter or cold battery. The rover that the Apollo astronauts drove on the Moon used wax for itself, the astronauts used sublimation (1, 2) for their suits.
    – uhoh
    Commented Feb 27, 2020 at 1:25

It is certainly possible to retrofit air conditioning to cars, as long as they have the electrical capability to support it (or you upgrade the alternator too). Lots of classic cars are now using this method. You can buy kits or see an example for instance of all the individual components: from various suppliers


For a ratty old pickup truck that lost all of its R-12 from a leaky condenser, the cheapest fix was a supermarket-grade window air conditioner, an inverter that I already owned and some welding cable for the battery hookup. The factory original 140 amp alternator provided plenty of power.

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The 4000 BTU/hour (4.2 MJ/hour) A/C provided plenty of cold air.

enter image description here

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    4000 BTU sounds a little light for a car -- built-in car air conditioners tend to be in the 20,000 - 60,000 BTU range. Though my big worry about the pictured air conditioner is what would happen in a crash as it tears through that bracing and makes its way out the front windshield. Better hope your head's not in the way.
    – Johnny
    Commented Feb 25, 2020 at 16:49
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    @Johnny The pickup had a short cab, so with this very small volume, 4000 BTU was plenty. (I received comments like "so cold you could hang meat".) Car A/C that's rated 20K-60K BTU is probably rated at cruising speed and produces much less cooling at idle or in stop-and-go traffic, but is still adequate. This unit ran on 120V so it was not derated by reduced engine speed. Crashworthiness? Not so much, but there was never a passenger in the middle seat.
    – MTA
    Commented Feb 25, 2020 at 18:17
  • Until the unit rattled itself apart from the vibration and bumps of driving. Commented Feb 26, 2020 at 2:31
  • I've edited for SI units, but why is the A/C measured in energy rather than power?
    – gerrit
    Commented Feb 26, 2020 at 8:55
  • @gerrit Thanks for that. I've added "per hour" to your edit. It's commonplace in U.S. marketing to refer to air conditioners as X BTU, though incorrect. BTU/hour is the correct term for cooling power. For further vexation, larger units are described in "tons", which refers to the cooling power of a ton of ice. Silly, but tradition is hard to change. One "ton" of cooling power is 12,000 BTU/hour.
    – MTA
    Commented Feb 26, 2020 at 13:49

Some of these might work:

(Essentially google rv or truck dc air conditioning)


but anything that runs out of a cigarette lighter and/or doesn't vent to the outside is almost certainly a rip-off--It's either evaporative (if it doesn't vent) or won't do much cooling (if it's 12v).

AC takes a lot of electricity and cannot "Cool" air, it can only move heat from one place to another (From inside your car to outside, for instance)

edit/irrelevant note:

Now that I think of it though--if one really wanted to create an air-conditioner for a car with a design that made use of the high flow of wind outside the car as part of it's energy (Perhaps use a really low-power heat exchanger and use the car's movement to power all the airflow) one could probably do it pretty well. It's probably just never been worth it because running a built-in AC is so much more efficient/cheap.

Also, In the mid last-century (am I really that old?!?) after-market AC units that were wired into the engine like stock ones were somewhat popular for a while--you don't really see them any more, again probably a lack of demand.

  • after-market AC units +1. Yes, we're that old and no one does this anymore because AC is standard on cars that cost more than a gen-set.
    – Mazura
    Commented Feb 25, 2020 at 23:45

The long road: A factory retrofit

First you skill up some electronics chops. This will be Very, very heavily electronics oriented.

Then, you get the schematics for your car, and you evaluate how the A/C normally wires into this car, particularly into the Powertrain Control Module and Body Control Module. Your objective is to determine whether your PCM and BCM can support air conditioning, and if not, whether it's practicable to change to a PCM and BCM that does. You may have to get into some programming to query or set the two computers to support A/C. If the A/C system gets into CANbus, then you've really got a job of it.

Then, you need to explore the car's wiring harnesses to make sure the necessary A/C wires are part of that harness. If not, you'll need to either retrofit them or make sure an A/C harness can be swapped in. For instance your vent/fan control may have a site for an A/C button; the question is whether the wires that go to that button are in the harness!

Then you'll need to change the vent control panel to support A/C. On newer cars this may involve fooling around with the Body Control Module (BCM).

You'll also need to make sure the wiring is there to support the A/C clutch, pressure sensor, and additional fans and relays (if used). You already determined that the PCM will support those if they're present.

At this point, you use resistors, LEDs and switches to rig up a "test setup" - make the car think all the A/C equipment is present, and see if you can get the car's computer to command the A/C system to cycle. It is very much in your interest to do these tests before doing any more work; because if you can't get the computer to command the A/C system to cycle, it's not going to work when you install it for real and charge it with freon.

At this point your car knows the way to the you-pick-your-part yard by heart.

If needed, you pull wiring harnesses (carefully, and completely) from junk cars. Do not cut and splice wires; that is unreliable. I saw someone buying a harness where the picker cut 30 wires because it was easier than taking a fender-well all apart. Now there'll be 30 crimps (60 connection points) up inside a fender well. Within a year one of them will fail. Forget that.

Then you find a suitable donor car and pull all the stuff:

  • The air conditioning evaporator (goes under the dash)
  • Heater core if your car uses a different heater core for A/C cars
  • Heater duct box if that is different on your car
  • The accumulator
  • The compressor and bracket
  • Any other parts needed to make room for the A/C compressor
  • The A/C condensor (sits in front of the radiator)
  • The larger radiator used on A/C cars
  • The fan assembly used on A/C cars, possibly with an extra fan
  • All piping connecting all of the above
  • All grommets and strain reliefs holding all piping
  • The A/C clutch relay

The picking yard will, at some point, have punched a hole in the system to bleed it. That means one pipe will be damaged. You'll need to find another car where the damage is on a different part.

Now, you assemble the whole kaboodle, with great care, ship-shape and in Bristol fashion. When an opportunity for a shortcut presents itself, like skipping a difficult-to-install grommet, set that emotion aside and do the job properly. The factory didn't put that grommet there for fun; they did it because it broke if they didn't.

Now off to the mechanic to get the system seal-tested and charged with freon. If you did your electrical testing earlier, the mechanic will repair any flaws in your work, and the system should spring to life.

The shorter, but more custom-fit road: aftermarket or marine

They make aftermarket kits for retrofitting A/C onto classic cars. They also make kits for installing A/C onto boats. Here, you'll have some of the work done for you; fair chance you can use a factory evaporator made for your car.

If you can get an A/C system that runs on 12V electric, you'll need a gigantic aftermarket alternator, but you can do that.

Don't waste your time with residential grade anything

The "Residential A/C unit + inverter" isn't going to work. The extremes of vibration, dust, and temperature that automobiles are exposed to, will murder the unit in short order.


Back In The Day (tm) air conditioning was an expensive option on a car. But people wanted air conditioning for their cars without paying the car manufacturers price, so other companies produced add-on air conditioning units that fitted beneath the dashboard of cars (which, back in the day, didn't go all the way down to the floor of the car). I remember seeing these units for sale at department stores like Sears, which would also handle the installation. And they worked well. My father worked for Eaton Corporation, which produced these units, and they always put one of their own units into whatever company vehicles they had. Dad used to buy the used company cars (they didn't get used very hard, and they got new ones every two years) so I remember using these when I was a kid.

And it looks like they're still available - see here: https://www.oldairproducts.com/products/ac-systems-parts/custom-street-rod-universal/underdash-systems?showpage=1


Well, actually you can. The concept of air-conditioner is to circulate air inside a closed room or space by adding some cold air, depending on the temperature you set.

Theoretically, you can create a small circulation inside your car using a mobile electronic fan but first, you will need to remove the hot air trapped inside your car. As for the cold air part, some fans now come with a built in mist release. Pour in some cold water so that you have your own source of cold air inside the car. It may not work accurately like a normal air-conditioner, but at least you have your mobile air-conditioner.

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    NO, that is a fan, or a swamp cooler, NOT an air conditioner.
    – Aron
    Commented Feb 24, 2020 at 7:03
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    this is a very good way to heat up cold water but it has nothing to do with an aircondition,and it might not be a good idea to have the water sloshing around inside a car. Commented Feb 24, 2020 at 7:06
  • @Aron Exactly - and a swamp cooler won't work (and will make life even more miserable) if it's already humid
    – costrom
    Commented Feb 24, 2020 at 15:10

And they do exist - only not in "mobile form" - but many cars have build in AC - using little amount of fuel and direct coupling to the running engine plus a refillable (in repair shops) liquid to provide cooling effect - nice side is the air is dried, so it even helps in humid conditions

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    The OP is specifically asking about units that could be used if his car doesn't have a built-in AC.
    – Nick C
    Commented Feb 24, 2020 at 16:37
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    This is a case of reading the title, coming up with a "Funny" answer based on the title alone and not taking the text of the question seriously (or possibly even reading it). It was my first thought when I read the title too.
    – Bill K
    Commented Feb 24, 2020 at 18:33

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