Turn the AC off before you shut the car off?
- Thread starter buster
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Kestas
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I think it's locked out during cranking when you start up the car. But otherwise it'll be on immediately after when the engine is trying to warm up. I don't think it's that bad.
One other thought is that some people turn their a/c off for the last minute of driving. This gives the evaporator a chance to dry off and prevent the formation of mold, which smells bad.
One other thought is that some people turn their a/c off for the last minute of driving. This gives the evaporator a chance to dry off and prevent the formation of mold, which smells bad.
My wife too. I don't expect to care her just, enough to drive in high traffic rush-hours with children, etc.
Her GM car is a cheap one, but after starting the car with A/C on: the compressor starts after some delay not to overload the engine.
So, the car takes care about itself.
Her GM car is a cheap one, but after starting the car with A/C on: the compressor starts after some delay not to overload the engine.
So, the car takes care about itself.
JHZR2
Staff member
My father always shut off all loads before turning off the car. Always makes sure to never draw load (lights, etc) with the car off.
10 years on a battery is the rule, not the exception.
Modern cars should be ok cranking with the AC on. Bigger concern is every extra ampere drawn from the fan (which IME does come on right away on all cars), causing more voltage drop.
To me the bigger question is of mold and how to prevent it. To me that is to turn off the AC with fan blowing. Thing is, on humid days, this means the interior of the car gets damp, which could mean mold elsewhere in time.
10 years on a battery is the rule, not the exception.
Modern cars should be ok cranking with the AC on. Bigger concern is every extra ampere drawn from the fan (which IME does come on right away on all cars), causing more voltage drop.
To me the bigger question is of mold and how to prevent it. To me that is to turn off the AC with fan blowing. Thing is, on humid days, this means the interior of the car gets damp, which could mean mold elsewhere in time.
I alway turn everything off before shut the car off.
I shut down the AC compressor about one block before my garage. I do this so to not have nasty water dripping on the garage floor. I shut everything else off before turning off the engine.
Originally Posted By: buster
My wife never turns the AC off before shutting the car off. So when you start the car up the next day, it immediately goes on. Is that bad?
My wife has done the same thing for decades. Aside from an AC hose going bad that's about the worst problem we've ever had with AC. I turn everything off.
My wife never turns the AC off before shutting the car off. So when you start the car up the next day, it immediately goes on. Is that bad?
My wife has done the same thing for decades. Aside from an AC hose going bad that's about the worst problem we've ever had with AC. I turn everything off.
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I always shut everything down before shutting off, especially the A/C. I do that to try and prevent mold and mildew. About a mile from home I'll turn the A/C to vent and blower on high.
I was was taught that was best for pretty much everything.
I was was taught that was best for pretty much everything.
Later model saturns come with "afterblow" where the HVAC fan runs for a minute with the engine off, to clear out the AC system.
As said above, the compressor clutch is engaged by the PCM a few seconds after the engine catches. On some cars (dodges) the PCM controlled alternator takes that long to come to life as well!
As said above, the compressor clutch is engaged by the PCM a few seconds after the engine catches. On some cars (dodges) the PCM controlled alternator takes that long to come to life as well!
Based on the design of most cars evaporators there is no way a minute or two off is going to significantly dry the coils. Just not going to happen.
But if you really believe it's true...
But if you really believe it's true...
I can't see it making a real difference.
JHZR2
Staff member
It would be nice to prevent moldy odors.
It won't matter if you leave it on or off for parts wear and tear.
Sometimes, it may be a good idea to turn the vents [and thereby the AC system]to 'OFF', to preserve your cool inside temps a little longer. [outside air can't mix in]
Sometimes, it may be a good idea to turn the vents [and thereby the AC system]to 'OFF', to preserve your cool inside temps a little longer. [outside air can't mix in]
Originally Posted By: SteveSRT8
Based on the design of most cars evaporators there is no way a minute or two off is going to significantly dry the coils. Just not going to happen.
But if you really believe it's true...
Agreed, on a hot day I want the AC on as soon as the engine starts...
Based on the design of most cars evaporators there is no way a minute or two off is going to significantly dry the coils. Just not going to happen.
But if you really believe it's true...
Agreed, on a hot day I want the AC on as soon as the engine starts...
For once, I'm going to have to agree with everybody else on here. The owner's manual for my PT Cruiser says that the AC doesn't kick on until the engine has been running for about 10 seconds. On old cars, I don't think it was good to start the car with the AC on but on the newer cars, it doesn't matter.
On my 60's era GM cars like Impalas and Chevelles the AC clutch was not energized until the key was released, so there was no drag on the start up.
Originally Posted By: MetalSlug
I alway turn everything off before shut the car off.
+1 Just for good measure. Maybe I am crazy but when I have the fans/AC up when I start the car it seems that the engine takes longer to crank. Good chance I am crazy.....
I alway turn everything off before shut the car off.
+1 Just for good measure. Maybe I am crazy but when I have the fans/AC up when I start the car it seems that the engine takes longer to crank. Good chance I am crazy.....
never turn off my a/c. until the weather changes anyway.
^^^Hahaha, I don't think it has EVER been off in my car!
No thank you. When it is 105F outside you feel the sunlight cooking you within 30 seconds of turning the AC off. I can deal with heat a lot better than cold and this has always been the case, but the last thing I want is to a have a nice layer of lather once I step out of my vehicle.
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