Run A/C with Windows Open?

For years my friend Sheldon and I have been having a debate over whether it is okay to run a vehicle’s air conditioner with the windows or convertible top down.

Sheldon believes it puts excessive wear on the air conditioner compressor and he will always turn off the air conditioner if the windows or convertible top is down. We live in Florida so he often has the convertible top down.

I on the other hand believe it is fine to run the A/C with either the windows or convertible top down. My reasoning is my Honda Accord has an automatic temperature control (ATC) system in the cabin and no where in Honda owner’s manual does it recommend turning off ATC while the windows or sun roof are open in the summer.

Tom and Ray please help! There is a dinner riding on this for the person with the correct answer and it is hot riding in my friend’s car.

Thanks much!


T&R never answer here, but you’ll get plenty of other opinions. No harm done with the windows open, except for the waste of gas involved. I don’t understand the ‘excessive wear’ argument - no more wear than when it’s running with the windows closed.

Agree with texases answer, but why run it in the first place? Perhaps the folks who wrote your Honda owner’s manual assumed that any normal person would not use the A/C with the top down or windows open.

It does make sense the open the windows after your car has been sitting in the hot sun and drive it a short distance to let that hot air our before you turn the A/C on, with the windowns closed, of course.

Any device has a service life, so when you run the air conditioner more than necessary, you are hastening the demise of your A/C system. What I don’t understand is why you would want to run it with the top down. It wouldn’t cool the cabin at all. The benefit wouldn’t be worth the cost in my opinion.

If you were a smoker and wanted to keep a window cracked, it would make sense to run the air conditioner. There would be an appreciable benefit. However, with the top down, you are doing nothing more than burning extra fuel.

No manufacturer should need to tell you to turn off your A/C with the top down. It is logical to assume if you have the top down, the weather is nice enough that it shouldn’t be necessary to run the A/C. Why would you put the top down if the weather so stifling hot that you think you need the A/C? Why not just leave the top up and be more comfortable?

Windows down ok

Top down no

It makes no difference at all. Here is why.

When the AC is on, and it is not on maximum, it pulls all the air that it cools and dehumidifies from the outside. (Only on maximum does it recirculate.)
Since it is pulling all the air from outside anyway, it doesn’t matter if the windows are open, or if the top is up. The only difference is that you don’t get most of the benefit from the AC. Either way, it works at exactly the same effort.

It won’t hurt either way. It is the same amount of wear as if the compressor was running and the windows up. I have a friend who does this, his reasoning is cool air in the face and nice weather circulating about in the cabin.

Why run the A/C when it’s doing nothing other than wearing itself out and burning a considerable amount of fuel?? Top down? Windows down? Turn the climate control off.

I can’t answer for the OP. In my case, it’s my money and my comfort. The mileage difference is a mile or two per gallon at the most. If money were more important than comfort, I probably drive a different car anyway.

Back the truck up Caddyman, I said it is a friend of mine and I cannot answer for him. I am also not saying he is right or wrong but it is a still a semi-free country so he can do as he pleases. Todays vehicles are to the point that there is a very small mileage difference with or without the a/c on.

AC on, top down,about 75 ambient (like at early night here in Tucson) thats what know as living good,very comfortable.

Turn the wipers on too…You don’t need them, but you paid for them so you might as well use them…Most cars have about a ton of air conditioning and you can’t run that kind of cooling for free…

What I don’t understand is why you would want to run it with the top down. It wouldn’t cool the cabin at all.

It depends on the car. My Miata did a nice bubble of air even on the freeway as long as there was a deflector behind the headrest. I could top down in the winter and still stay warm.

That said, I seldom did it and running the AC will reduce mileage and may reduce the A/C life a little also. But if it was all about money and not comfort and a desire to go topless why would anyone have a convertible or an A/C in there car?

If it was all about money why would anyone buy a car with A/C?

If it was all about money why would anyone buy a car with A/C?

The OP lives in Florida, Joseph. Here in Florida, A/C isn’t just about comfort. It is for being able to get from one place to another and not die of heat stroke or arrive dripping with sweat.

The question is, who would be crazy enough to NOT buy a car with A/C and live in the state of Florida? I know some people do it, but trust me, they are miserable.

80% of the vehicles sold in Alaska have A/C…But that’s not what this thread is about…

A GM instructor gave a figure of the same capacity exists in a Suburban as does a 3 bedroom house.

Some (ATC) have the ability to simply open the vent when the system is off. Our Subaru Legacy GT does if click the the air flow position button with the automatic climate control system off. The fan does not run but the air flows in and a graphic of just the arrows for flow appears on the control. I think Honda would have the same.

Good posting, tardis. My exact thoughts. I am amazed how few people understand what the word, liberty, really means. Alexis d’tocqueville in DEMOCRACY IN AMERICA, early 19th Century reported greater personal freedom in dictatorial France than in the US, because in the US it was one’s neighbors, not the government, who made life miserable for non-conformists.

Those who think with open windows or top down, a/c will do no good need to try it once. With a very hot day, the sun right overhead, the sun’s heat will control, but in many circumstances, yes, you can feel the cold bubble in the front seat. Simple laws of physics.

“The OP lives in Florida, Joseph”

I understand what you are saying, and I certainly would not own a car without AC in Florida, but there was a time cars did not have AC and they still used them in Florida. I’m old enough to remember that. So if it really is all about money, then …