So a little back story my dad always taught me growing up to cut off the a/c before you turn the car off. He said it makes everything last longer and it will prevent leaks in the system in the future. Well it is now 2019 I have two new vehicles with auto climate and a older 99' f250. I religiously turn the a/c off in the ‘99 f250 but leave everything set to auto in the new vehicles. I wanted some further input as I didn't know if any of this even mattered. It's now just a habit more than anything....do the pressures equalize faster/better when turning it off? Anyways thanks for reading as I have wondered this and never thought to ask! Thanks
Cutting off A/C before Car
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The ac is computer controlled in everything these days. No reason to turn it on or off before starting or stopping the engine.
It depends on the vehicle. I shut off the A/C on our 07 Accord 3-4 min before our destination. On our '13 Subaru we don't. That prevents a moldy, sour smell in the Accord. The Subaru doesn't have that issue, but the A/C drain did plug once (which never has happened on the Accord)
When I can remember, I shut off the AC on my vehicles a few miles before stopping, but I keep the fan running. This circulates air around the AC evaporator and helps to dry the unit, limiting the growth of mold and preventing the development of that musty AC smell.
The hardest part is remembering to do it and convincing the wife to do it.
The hardest part is remembering to do it and convincing the wife to do it.
I still shut things off before I turn off the car because Dad taught me to. But my understanding is that it is all computer controlled these days so it doesn't matter.
I don't remember which car, and it was years ago, but I remember a owners manual saying leaving it in the recirculate or off position would leave the vent doors closed which could slow or even trap the condensation. Most cars I've own would maintain enough vacuum right after shutdown I could here the vent doors open after changing from one of those settings. Might be a non-issue on newer cars.
Turning off the AC when the car is off vs running doesn't make a difference. The AC is off as long as the compressor isn't engaged.
The main benefit for turning off the AC before you come to a stop is to dry the evaporator. This can prevent mold and mildew build up.
As for computer controlled, yes a computer controls them. But there inputs are still based on pressure and temperature. Cars have a low/high pressure switch and a low side temperature sensor.
"Auto" mode relates to regulating interior temperatures. Interior temperature is controlled by moving blend doors, and changing blower speed. Not by changing how often the compressor cycles.
The main benefit for turning off the AC before you come to a stop is to dry the evaporator. This can prevent mold and mildew build up.
As for computer controlled, yes a computer controls them. But there inputs are still based on pressure and temperature. Cars have a low/high pressure switch and a low side temperature sensor.
"Auto" mode relates to regulating interior temperatures. Interior temperature is controlled by moving blend doors, and changing blower speed. Not by changing how often the compressor cycles.
It doesn't matter, And never did in my opinion.
I don't remember ever pulling a Evaporator Core that was covered in mold......Dirt/Dust/Straw wrappers/Gum wrappers/Condom wrappers/Hair....Pet & Human/Candy wrappers etc are fairly normal though.
I don't remember ever pulling a Evaporator Core that was covered in mold......Dirt/Dust/Straw wrappers/Gum wrappers/Condom wrappers/Hair....Pet & Human/Candy wrappers etc are fairly normal though.
Waaaaaaaaaaaay back when. If the AC was left turned on and you started the car. The instant you turned the key on the clutch engaged on AC compressor. So the starter was cranking the engine and the compressor. I believe this is where the turn off the AC thing started.
Originally Posted by clinebarger
It doesn't matter, And never did in my opinion.
I don't remember ever pulling a Evaporator Core that was covered in mold......Dirt/Dust/Straw wrappers/Gum wrappers/Condom wrappers/Hair....Pet & Human/Candy wrappers etc are fairly normal though.
I'm not sure I want to know how a condom wrapper makes its way into the evaporator core, but my own morbid curiosity is getting the better of me...
It doesn't matter, And never did in my opinion.
I don't remember ever pulling a Evaporator Core that was covered in mold......Dirt/Dust/Straw wrappers/Gum wrappers/Condom wrappers/Hair....Pet & Human/Candy wrappers etc are fairly normal though.
I'm not sure I want to know how a condom wrapper makes its way into the evaporator core, but my own morbid curiosity is getting the better of me...
Cutting off A/C early (but keeping the blower running) mainly reduces moisture in the system to slow down fungus growth.
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To clarify my earlier post... In the summer the AC is left on continuously except occasionally when its not needed, in which case the vent is run. I guess this would dry out the condensation and kill off any fungus. But the answer to the original poster remains... you can just leave the AC switch on continuously for days if necessary and it won't be an issue. But do run the vent any time you don't really need AC.
Originally Posted by A_User55555
The main benefit for turning off the AC before you come to a stop is to dry the evaporator. This can prevent mold and mildew build up.
THIS - living in the humid South, you learn the importance of this habit.
The main benefit for turning off the AC before you come to a stop is to dry the evaporator. This can prevent mold and mildew build up.
THIS - living in the humid South, you learn the importance of this habit.
I doubt it makes any difference. Circulating the refrigerant w/oil around in the winter does help but I believe many vehicles turn on the A/C in defrost mode.
I live in Houston and never turn the AC off. Have yet to have a mold or smell issue, LOL. Some of you overthink things a bit too much, I think.
I too have been one of those that turns off the fan and AC before shutting the car off, though recently it may all just be on full blast upon both shutting off and turning on the car. My practice may have been from a car where somehow electrics were still going to be running or drawing power even after the car was off, some belief that if it is off it can't kill a battery, or some belief of that it can't overload the system upon turning it on, or something like that.
The AC and its gas are going to circulate for a short time after shut off whether you do it or the car does and the moisture usually comes out as water moreso after the car is turned off, whether that is ice melting from an undercharge (the cabin still ice cold so, whether it is or it is not is irrelevant) or that's just the condensed water coming out more same as a runner that just ran in the heat and all the sweat pours out, just the same as early shut off or not. Though I have done this. Though I may stop doing this.
Had a few cars with automatic everything and if that is working properly then leave it all on, it even turns off the cigarette lighter power so that can't drain. Smart.
The AC and its gas are going to circulate for a short time after shut off whether you do it or the car does and the moisture usually comes out as water moreso after the car is turned off, whether that is ice melting from an undercharge (the cabin still ice cold so, whether it is or it is not is irrelevant) or that's just the condensed water coming out more same as a runner that just ran in the heat and all the sweat pours out, just the same as early shut off or not. Though I have done this. Though I may stop doing this.
Had a few cars with automatic everything and if that is working properly then leave it all on, it even turns off the cigarette lighter power so that can't drain. Smart.
Originally Posted by Skippy722
Originally Posted by clinebarger
It doesn't matter, And never did in my opinion.
I don't remember ever pulling a Evaporator Core that was covered in mold......Dirt/Dust/Straw wrappers/Gum wrappers/Condom wrappers/Hair....Pet & Human/Candy wrappers etc are fairly normal though.
I'm not sure I want to know how a condom wrapper makes its way into the evaporator core, but my own morbid curiosity is getting the better of me...
I'm reminded of Robin William's quote about how much blood God gave to man--I'll leave it at that.
Originally Posted by robertcope
I live in Houston and never turn the AC off. Have yet to have a mold or smell issue, LOL. Some of you overthink things a bit too much, I think.
Must depend on the car. I don't think I've had a car yet that didn't suffer from the problem. All of them, once I turn off the a/c and turn off recirculate a couple miles from home, there is that smell. And it's there the following day too. Once I stop using a/c the smell dies off and goes away... until next season.
Originally Posted by clinebarger
It doesn't matter, And never did in my opinion.
I don't remember ever pulling a Evaporator Core that was covered in mold......Dirt/Dust/Straw wrappers/Gum wrappers/Condom wrappers/Hair....Pet & Human/Candy wrappers etc are fairly normal though.
I'm not sure I want to know how a condom wrapper makes its way into the evaporator core, but my own morbid curiosity is getting the better of me...
I'm reminded of Robin William's quote about how much blood God gave to man--I'll leave it at that.
Originally Posted by robertcope
I live in Houston and never turn the AC off. Have yet to have a mold or smell issue, LOL. Some of you overthink things a bit too much, I think.
Must depend on the car. I don't think I've had a car yet that didn't suffer from the problem. All of them, once I turn off the a/c and turn off recirculate a couple miles from home, there is that smell. And it's there the following day too. Once I stop using a/c the smell dies off and goes away... until next season.
I haven't turned off my A/C ever. Just adjust temperature as desired.
If I turned the A/C off even a few minutes before stopping, I'd roast.
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