# How do I get my window AC to work when it's cool outside? **URL:** \ **Category:** Factual Questions\ **Created:** [September 26, 2016, 12:20pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921 "2016-09-26T12:20:46Z")\ **Posts on this page:** 18\ **Page:** 2
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [September 26, 2016, 9:01pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/21 "2016-09-26T21:01:37Z")
Can’t you just turn the furnace fan to on (without starting the furnace)? That will suck outside air in through the furnace filter, and blow it out of all the vents in the house. That’s what I do in the Fall – even sometimes in the Summer, when it cools down enough at night. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [September 26, 2016, 10:05pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/22 "2016-09-26T22:05:32Z")
> [@t-bonham@scc.net](#): > > Can’t you just turn the furnace fan to on (without starting the furnace)? > That will suck outside air in through the furnace filter, and blow it out of all the vents in the house. That’s what I do in the Fall – even sometimes in the Summer, when it cools down enough at night. Your furnace shouldn’t be drawing in air from outside. Many people run the fan to help cool themselves, but only because it circulates the air. It moves air from lower parts of the house where it’s cooler to higher parts (or even just lower in the room to higher in the room) and it creates a air movement which cools you off. But I don’t think most (any?) furnaces are designed to pull in outside air, maybe with the exception of some cutting edge green units, but none that I’ve heard of. Just so we’re on the same page, some furnaces do have a small intake from the outside (not counting a sealed combustion intake), but that’s for making up air removed by things in your house like bathroom or stove exhaust vents. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [September 27, 2016, 1:28am UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/23 "2016-09-27T01:28:34Z")
> [@Joey\_P](#): > > Many people run the fan to help cool themselves, but only because it circulates the air. It moves air from lower parts of the house where it’s cooler to higher parts (or even just lower in the room to higher in the room) and it creates a air movement which cools you off. It equalizes temperature throughout the house and makes it more comfortable. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [September 27, 2016, 1:44am UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/24 "2016-09-27T01:44:52Z")
Buildings can’t retain so much heat to moderate the temperature over several weeks unless you’re talking about enormous heat sinks (like swimming pool size tanks of water or huge masses of concrete). Even several days is a stretch with thick wall adobe construction that’s meant to store heat but still only shifts the temperature fluctuations by about half a day. So no, the building is not retaining heat from all summer, there must be other heat sources like a lot of incandescent lights, computers, old TVs, or who knows what. If the a/c isn’t cooling at all then there probably is a low-temperature cutoff of some sort to protect it. Conversely, if there isn’t a cutoff, it could be that the evaporator is icing up and blocking the air flow. Babysitting the system to make sure it shuts off and melts the ice is tedious, and with a residential unit you don’t want to go blocking airflow through the condenser outside to keep the temperature up without risking damage to the fan motor or compressor. No window units or central furnaces take in enough outdoor air to be effective at cooling. The largest I’ve ever seen in a window a/c is about one square inch, and with a central system maybe a 5" duct at best. That’s nothing. There are systems out there with what are called economizers, which close off the return plenum and then intake the air directly from outside, but those are sizable boxes with an outdoor intake grille as big as a window, and they require an exhaust damper and other controls that you don’t find in residential systems. If you do open up the house though, running the furnace fan with all your filters will help clear out any particulates, after you close the windows again. I don’t think you’ll gain much by doing it when the windows are open, but it wouldn’t hurt either. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [September 27, 2016, 8:01am UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/25 "2016-09-27T08:01:03Z")
> [@t-bonham@scc.net](#): > > Can’t you just turn the furnace fan to on (without starting the furnace)? > That will suck outside air in through the furnace filter, and blow it out of all the vents in the house. That’s what I do in the Fall – even sometimes in the Summer, when it cools down enough at night. There’s no ductwork in the house. It used to use a furnace connected to radiators, and then was converted to electric baseboard heat. ---
**Author:** ![Jesta](https://avatars.discourse-cdn.com/v4/letter/j/c5a1d2/32.png) [@Jesta](https://boards.straightdope.com/u/Jesta)\ **Post date:** [September 27, 2016, 10:41am UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/26 "2016-09-27T10:41:25Z")
Here’s a guide to the window fan\filter setup… > **[DIY Twin Window Fan Air Filter](http://www.air-purifier-power.com/windowfanfilter080515.html)** > > A do-it-yourself window filter, under $100... “Done correctly, this will keep lots of dust out of the house. I believe savings on HEPA filters and AC will more than compensate for the cost (under $100 for this fan and filters).” ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [September 28, 2016, 1:09am UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/27 "2016-09-28T01:09:05Z")
> [@SlackerInc](#): > > I mean, I do go outside\*, so it doesn’t have to be boy-in-the-bubble. > > \*Although if I’m suffering pretty bad by the time I get home, I immediately strip off my clothes, put them in one of the plastic bags I keep near the door, and jump in the shower. I’m sorry the answer we were looking for was “Moops.” ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [September 28, 2016, 1:34am UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/28 "2016-09-28T01:34:47Z")
LOL 😛 > [@Jesta](#): > > Here’s a guide to the window fan\filter setup… > > [DIY Twin Window Fan Air Filter](http://www.air-purifier-power.com/windowfanfilter080515.html) > > “Done correctly, this will keep lots of dust out of the house. I believe savings on HEPA filters and AC will more than compensate for the cost (under $100 for this fan and filters).” Nice! Thanks. ---
**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\ **Post date:** [September 28, 2016, 3:47pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/29 "2016-09-28T15:47:12Z")
Buy an old window air conditioner with mechanical knobs - not electronic controls. The old units used to work no matter how cold it was outside. The new ones seem to have some sort of switch which disables them when it gets into the 60’s and below outside. Note some rooms like computer rooms need air conditioning year round. Also large auditoriums - each person puts off around 600 Btu’s of heat - x 10,000 people! I don’t know why they don’t consider these things when designing air conditioners? Homes have similar situations. And with high crime areas, turning on the A/C is safer than opening a window! ---
**Author:** ![I.Dunno](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I.Dunno](https://boards.straightdope.com/u/I.Dunno)\ **Post date:** [September 28, 2016, 3:59pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/30 "2016-09-28T15:59:37Z")
> [@Me\_Billy](#): > > Buy an old window air conditioner with mechanical knobs - not electronic controls. The old units used to work no matter how cold it was outside. The new ones seem to have some sort of switch which disables them when it gets into the 60’s and below outside. > > Note some rooms like computer rooms need air conditioning year round. Also large auditoriums - each person puts off around 600 Btu’s of heat - x 10,000 people! I don’t know why they don’t consider these things when designing air conditioners? Homes have similar situations. And with high crime areas, turning on the A/C is safer than opening a window! AC units for year round use are designed to be able to operate safely and efficiently in cold weather. Generally speaking, a simple way is to cycle and/or reduce the speed of the condenser fan(s). These are commercial units for large scale cooling. This isn’t usually necessary for home units and adds to cost and complexity. And I can’t think of a way that a window unit could be modified to operate in such a scenario, mainly because there is only one fan motor. ---
**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\ **Post date:** [September 28, 2016, 4:13pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/31 "2016-09-28T16:13:54Z")
Another option is to get a [portable, in-room AC unit](http://www.homedepot.com/b/Heating-Venting-Cooling-Air-Conditioners-Coolers-Air-Conditioners-Portable-Air-Conditioners/N-5yc1vZc4m4). These are standalone AC units that you put in a room to cool it off and it has hoses to direct the hot air outside. They come in one-hose and two-hose models. Because of your allergy concerns, you’d want a two-hose model. A one-hose model sucks air out of the room, which ends up drawing in outside air into the house. A two-hose model uses one hose to suck in air over the hot coils and then directs that air back outside. It keeps the outside air from getting in the house. Since it’s in the room, the outside temp wouldn’t affect its operation. ---
**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\ **Post date:** [September 28, 2016, 4:14pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/32 "2016-09-28T16:14:27Z")
> [@I.Dunno](#): > > …I can’t think of a way that a window unit could be modified to operate in such a scenario, mainly because there is only one fan motor. I have two different window A/C units - old with mechanical knobs (works when cool outside) and a newer electronic controls model. On my “to do” list to look at the electrical schematic of the newer model to see if there is an outside thermometer which senses it is cool outside or something similar? (And them modify it so it will work when cool.) Possible? ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [September 28, 2016, 5:32pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/33 "2016-09-28T17:32:51Z")
> [@I.Dunno](#): > > AC units for year round use are designed to be able to operate safely and efficiently in cold weather. Generally speaking, a simple way is to cycle and/or reduce the speed of the condenser fan(s). These are commercial units for large scale cooling. > > This isn’t usually necessary for home units and adds to cost and complexity. And I can’t think of a way that a window unit could be modified to operate in such a scenario, mainly because there is only one fan motor. I can’t speak for ACs, but plenty of store reefers and freezers with the condensing units outside will cycle some of their fans on and off to build up a bit of heat as well as using heating cable on the accumulator and compressor. This [the heat wire] prevents the refrigerant from migrating up there and making hard or impossible for the compressor to start back up the next time it needs to. If you really wanted to mod a window unit, well to be honest, I’d just bypass whatever switch isn’t allowing it to turn on when it’s cold (unless it’s a pressure switch) and see what happens. It’ll probably just blow out the compressor sooner rather than later. The proper way would be to get some heat wire (you can get it at Home Depot) and wrap it around the compressor body a few times. Of course, car ACs run just fine even in the dead of winter (in the majority of cars, the AC is on when your defroster is on). I’m not sure what they do differently. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [September 28, 2016, 6:59pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/34 "2016-09-28T18:59:19Z")
Not super cheap but this does exactly what you want if you must have over ride cooling. > **[Amazon.com: COOLBOT Gen6 2015-2019 (Blue) : Sports & Outdoors](https://www.amazon.com/COOLBOT-Gen6-2015-2019-Blue/dp/B07T32HF9H)** > > Buy COOLBOT Gen6 2015-2019 (Blue): Sports & Outdoors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases [![]( " - YouTube") ](https://www.youtube.com/watch?v=-vJ-AMsKZzk) ---
**Author:** ![ziper1221](https://avatars.discourse-cdn.com/v4/letter/z/a183cd/32.png) [@ziper1221](https://boards.straightdope.com/u/ziper1221)\ **Post date:** [September 28, 2016, 7:11pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/35 "2016-09-28T19:11:07Z")
> [@Amateur\_Barbarian](#): > > Probably more because the building slowly absorbs heat all summer and re-radiates it into the interior. It’s common for a house to stay cool for the first month of summer weather (and warm for the first month of winter) until the structure gains or loses enough heat to affect the interior even when nothing else is going on. This doesn’t sound right at all. There is no way a traditional house has that much thermal mass. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [September 28, 2016, 8:13pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/36 "2016-09-28T20:13:58Z")
> [@ziper1221](#): > > This doesn’t sound right at all. There is no way a traditional house has that much thermal mass. I agree that notion is ludicrous. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [September 28, 2016, 8:30pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/37 "2016-09-28T20:30:07Z")
> [@Me\_Billy](#): > > Buy an old window air conditioner with mechanical knobs - not electronic controls. The old units used to work no matter how cold it was outside. The new ones seem to have some sort of switch which disables them when it gets into the 60’s and below outside. I hate to be the “Actually…” guy, but of our seven air conditioners, one is an older digital model, one is a newer digital model, and the other five just have mechanical knobs. But those five are the balkiest in cool weather! The older digital one is only a little better, while the newer digital one–which has an actual numerical thermostat–is the most willing to kick on if you turn the thermostat number lower than the room temp it is reading. ---
**Author:** ![I.Dunno](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I.Dunno](https://boards.straightdope.com/u/I.Dunno)\ **Post date:** [September 28, 2016, 9:52pm UTC](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921/38 "2016-09-28T21:52:12Z")
> [@Me\_Billy](#): > > I have two different window A/C units - old with mechanical knobs (works when cool outside) and a newer electronic controls model. > > On my “to do” list to look at the electrical schematic of the newer model to see if there is an outside thermometer which senses it is cool outside or something similar? (And them modify it so it will work when cool.) > > Possible? IF you can find an outside air sensor and it is “binary”, i.e. a physical switch that is either CLOSED or OPEN, then you may be able to jump it out. However, if there is a thermistor or some other wholly electronic device, especially if it’s part of the circuit board, then it’s likely not possible. I’m a retired HVAC tech but window units, especially these new-fangled electronic digital controlled ones ain’t my thing. But good luck! [Previous page](https://boards.straightdope.com/t/how-do-i-get-my-window-ac-to-work-when-its-cool-outside/766921.md?page=1)