There is one benefit that lion9car touched on in the first page:
In addition, the air conditioner needs to be run regularly to prevent damage, so that eliminates having to worry about that
Running the A/C during times when most people would not even think about doing so helps to keep the seals exercised and prevent leaking. I would rather have it turn on automatically at times during a long winter to prevent leaks than to have to remember to do it myself periodically. Having owned a number of cars in the early years of A/C, I’ve come to appreciate the reliability of the systems in newer cars. If that means running it at times I would normally not choose myself, so be it. It would take a lot of gas savings to offset just one A/C repair…
I mentioned it before and others have–the A/C compressor needs to run some in the winter to keep the seals fresh. That is why it comes on when you turn on the defroster. Or I should say, one reason.
Seems a heck of a lot more economical to manually select a/c some nominal amount of the time (1X/month?) rather than every time I need defrost, which works out to every day, all winter long.
I wonder if a “no a/c unless specifically requested” setup would save more or less gas than all the “engine off at red lights” posts we’ve been getting, at far less collateral cost…
meanjoe75fan I don’t suppose economy would be an issue here, but You could get the ice off the windshield quicker if the A/C wasn’t running. Hot air melts ice faster than cooled air.
MikeInNH, says all of these cars did not turn the A/C on when defrost was turned on, I say most of them did. All the vehicles I have had for at least 40 years did use the A/C with the defroster. Does anyone know for sure, please help settle this.
87 Honda Accord
96 Accord,
90 Pathfinder
98 Pathfinder
05 4Runner
07 Lexus ES350.
66 Fleetwood
72 Ford F150. I don’t like to be proved wrong, but if I am, I am not to proud to admit it. I havent worked much on cars for a few years, there is a lot I don.t know.
For my first 20 years of driving no car I owned had AC, defrost worked fine. The last 20 years I have had AC that runs while defrost is on. I think you are making a problem where there is no problem. The heat output is fine and the ac dries out the air before blowing hot. Hot is still just as hot as far as I can tell.
Right now I can only attest to three vehicles. I checked these by opening the hood and visually checking the AC clutch, not going by the light in the switch, which BTW that light just tells you that the switch is on, not if the compressor is running.
97 Honda Accord, compressor does NOT run in defrost with the fan on or off.
97 Nissan Pick Up, compressor does NOT run in defrost with the fan on or off.
02 Saturn, compressor DOES run in defrost with the fan on, does NOT run in defrost with the fan off, does not run in the bi-level (windshield/floor) position with the fan on or off.
In the Saturn, if I want to defrost without the AC, I use the bi-level position.
My first car, a 1974 Cadillac, ran the A/C compressor when defrost was selected. Every subsequent car I’ve owned has done the same. Only the last 3 vehicles I’ve owned have had a separate switch for the A/C compressor–all the other vehicles operated the A/C when you selected specific A/C modes on the selector, or when you turned on defrost.
My last two vehicles will turn on the A/C with the defrost, and it cannot be turned off in any defrost mode. (except the rear window defroster) The manuals on my last several vehicles, and even as far back as a 1980 vehicle I had, stated that the A/C will run in defrost modes and will not run when the outside temp is ~35 degrees or cooler. I have verified this to be true. There may be some older vehicles that do not behave like this, but I haven’t encountered them.
I can tell you that the windshield clears a LOT faster with the A/C running, especially in rainy, humid weather. And you don’t need to have the heat blasting, cooking you, just to keep your windshield clear, as you need to do without A/C. So overall, I’d say it’s a pretty good idea for it to run automatically, especially as people as a whole are generally too ignorant these days to realize it should be turned on with defrost. People also don’t realize that their air should be set to outside intake and not recirculate when defogging their windows. So cars with climate control take care of this for you too.
My 1971 Ford Maverick with factory air did not turn on the compressor when “defrost” was selected. However, the 1975 AMC Pacer did turn on the compressor with the defrost as did my 1978 Oldsmobile. I have never thought about it in our later vehicles.
I do remember riding with a colleague in his 1963 Mercury Meteor years ago. The windshield kept fogging up. I suggested he turn on the air conditioner. He didn’t think it would do any good, but did take my suggestion. Almost immediately, the fog on the windshield disappeared.
". So overall, I'd say it's a pretty good idea for it to run automatically, especially as people as a whole are generally too ignorant these days to realize it should be turned on with defrost"
And that in a nutshell is why I don’t like the AC to come on automatically. I do know when it is needed and I don’t need someone else making that decision for me. Maybe you are not insulted when someone calls you stupid, but I am.
Well, I thot most cars the last 20 or 30 years ran the A/C with the defroster. It seems that just some of them did. I went out yesterday to see if mine did, but the A/C compressor is under the engine and I couldn’t tell if it was running. It was around 32 degrees.
I think you are worrying too much. Sure the first 20 years I drove I had no ac, but the temp blowing out the defrost is not significantly weather ac is on or off. The advantage is the air is drier when the ac kicks in. Let it do it’s thing and not to worry.
EllyEllis, you don’t need to see the whole compressor. just the front of the pulley. When the compressor is off, the front of the pulley is not turning, just the pulley itself. With the car in any position not involving defrost and the blower motor on, check the front of the pulley with the AC on and then off and you will see.
Another thing is that in most, if not all vehicles, anytime the compressor is running, so are the front fans, so if the engine is cold, you turn on the defrost with the blower motor running and if the radiator fan(s) come on, the compressor is definitely on.
Something that seems to be a myth here is that if the incoming air is below 40°F, that running the AC will somehow dehumidify the air more. It does not, the AC can only dehumidify down to the dew point of around 40°F plus or minus a few degrees. Any air coming into the cabin that is lower than that is already below that dew point for humidity.
And that in a nutshell is why I don’t like the AC to come on automatically. I do know when it is needed and I don’t need someone else making that decision for me. Maybe you are not insulted when someone calls you stupid, but I am.
So why do you think this is an assault on your intelligence personally?
As was mentioned by a number of people, the majority of consumers do not know this and even if they do, are too lazy to do it. It is in the interest of the manufacturer to cater to the majority especially if it impacts longevity of some expensive components. You should only be insulted if you’re in the aforementioned group.
Look at how many people don’t even check their oil level. If your next car came with an oil level warning light, would that be an insult to you personally? Heck, I don’t like TPMS but I don’t believe its common implementation is an insult to my intelligence…
TPMS is just a warning, the passing of information. I still decide whether to add air or not, and whether I want to use air or nitrogen. But the defrost position that automatically turns on the AC is taking the decision making process away from me. I also don’t like the automatic headlights or the automatic windshield wipers.
Well, Keith, I would rather have control of the A/C also, but on most vehicles we don’t. This morning my car was covered with heavy frost. I turned on the defrost and turned the heat up, but I think the A/C came on also.
Also, when I checked the A/C the other day with defrost on, all I could see was the end of the compressor and it was running. It was 19 degrees, if I remember right.
Auto wipers are interesting. Sometimes you think they aren’t gonna go, but then they do. Other times they go when you don’t really think they need to. It is kinda funny how they can go 5 seconds then 3, then 10, then continuous in a 1 or 2 mile stretch of road.
I would like to have intermittent setting on top of the auto setting, but my car doesn’t have that; one or the other depending on trim level.