Automotive

Leaving the Heat/AC on Turning off/starting the car

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  • Jan 25th, 2013 3:19 pm
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Leaving the Heat/AC on Turning off/starting the car

I've heard that it is best to not leave the heat/AC on when you switch on/off your vehicle due to fears of damaging the battery. Is this still true?
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No, but the draw from running the blower motor will cause an increased draw on the battery when starting the car.
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No. And odds are the blower motor doesn't run while the key is in the "Start" position.
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lennyandcarl wrote:
Jan 24th, 2013 8:51 pm
No, but the draw from running the blower motor will cause an increased draw on the battery when starting the car.
That feature has been missing from modern vehicles since the late 70's. ;)
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Thanks for the answers!

Here's a link that also talks about this issue.

http://boards.straightdope.com/sdmb/arc ... 16802.html

I've also noticed that for the times I've forgotten to switch off my fan/radio while I start my car, the fans and radio would shut off intermittently until the car has finished start up. I believe this is the feature to prevent the sudden load of battery usage as toyorav4me pointed out.
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I never turn my radio off (I have an aftermarket deck so it requires me to hold the button down when it has power) but I always turn my blower motor off prior to starting the car. Once the car is started I immediately put the blower on and heated seat.
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murdoc2k wrote:
Jan 24th, 2013 10:14 pm
Thanks for the answers!

Here's a link that also talks about this issue.

http://boards.straightdope.com/sdmb/arc ... 16802.html

I've also noticed that for the times I've forgotten to switch off my fan/radio while I start my car, the fans and radio would shut off intermittently until the car has finished start up. I believe this is the feature to prevent the sudden load of battery usage as toyorav4me pointed out.
You got it, modern electrical engineering at work. :)
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B.C.
toyorav4me wrote:
Jan 24th, 2013 9:35 pm
That feature has been missing from modern vehicles since the late 70's. ;)
More like the 90's....
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murdoc2k wrote:
Jan 24th, 2013 10:14 pm
Thanks for the answers!

Here's a link that also talks about this issue.

http://boards.straightdope.com/sdmb/arc ... 16802.html

I've also noticed that for the times I've forgotten to switch off my fan/radio while I start my car, the fans and radio would shut off intermittently until the car has finished start up. I believe this is the feature to prevent the sudden load of battery usage as toyorav4me pointed out.
This.. everything momentarily turns off when I start my car
ShadowVlican
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What about heated seats, should we be turning that off before starting the ignition? TIA.

I know that should be drawing a lot of current.
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alanbrenton wrote:
Jan 25th, 2013 11:13 am
What about heated seats, should we be turning that off before starting the ignition? TIA.

I know that should be drawing a lot of current.
The heated seat should have been turned off automatically when the engine was shut down and do not come on via the ignition switch ... so they should not need to be shut off ... or am I mistaken.

My assumption is that all electrical loads that are drawing current when the starter motor is engaged simply "dim" as the battery output drops a few volts. But perhaps the computer does disable loads like lights until the engine is running and generating again on out new clever vehicles.
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No issue with battery, but from what I understand, you'd want to turn AC off a few minutes before turning engine off to get rid off any condensation build-up. Otherwise you could get mold growth and a nasty smell in the cabin.
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Little Tim wrote:
Jan 25th, 2013 12:23 pm
No issue with battery, but from what I understand, you'd want to turn AC off a few minutes before turning engine off to get rid off any condensation build-up. Otherwise you could get mold growth and a nasty smell in the cabin.
Hmmm. This is food for thought. Is this only to be done during winter time or throughout the year? I play with my AC so won't have an issue but my wife keeps her mostly on.
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alanbrenton wrote:
Jan 25th, 2013 12:38 pm
Hmmm. This is food for thought. Is this only to be done during winter time or throughout the year? I play with my AC so won't have an issue but my wife keeps her mostly on.
I assume there will be less condensation issues in the winter. It's in the summer that you will have the hot air hitting the cool vent ducts and the evaporator and you would get condensation. However, I still turn off the AC (defroster) a couple of minutes before stopping in the winter anyway just to keep the habit going.

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