air conditioning on / off

I was driving this morning using the a/c and remembered what my dad told me many years ago and wondered if that was still good advice. He said that you should turn off the a/c before you turn off the engine.
Likewise you should turn on the engine before you turn on the a/c. Is this still good advice in the modern age ?
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4ax.com:

Makes no difference these days.
What /does/ make a significant difference is shutting the A/C off (but leaving the ventilation fan on) ten minutes or so before parking the car for a long time. This way, you help the evaporator shed some of its moisture before shutdown, reducing the buildup of mold and the resulting "stinky-socks" smell.
--
Tegger

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On 06/10/2010 09:53 AM, Tegger wrote:

use of cabin air filters has pretty much eliminated that problem.
--
nomina rutrum rutrum

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I thought the reason for running the fan with the A/C off was to try and dry out the evaporator drain pan so there wouldn't be any moisture that promotes mold growth (at least here in the sunny south). I can't see how having a cabin filter effects that "theory" one way or the other.
Also, I have to wonder about how useful the filters are. All our RAV4's have them, my Nissan Frontier had one. My son's Mazda has one. I changed them all in the last month or so. They all fit so loose in the compartment that there are gaps on the sides that it seems to me would allow some stuff to slip by (no idea how much and whether it is significant). The old filters were all full of litlle tigs and unidentifiable "stuff" when I changed them. At least for my Frontier they didn't seem to stop dust and they didn't stop the pollen that watered my eyes in one particualr location I drive through regularly (a swampy area I have no idea what is there, but at certain times of the year, driving through the area makes me cry).
Ed
Ed
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On 06/10/2010 12:15 PM, C. E. White wrote:

dust sticks to cold [damp] evaporators much more than dry ones. eliminate the dust, and there's no accumulation to get moldy and smell.

personally, i don't understand why vehicle marketing departments bleat about these supposed "benefits". i'd install the filter to keep crap out of the evaporator, especially if it were aluminum. no other "explanation" required.

--
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wrote:

Doesn't it place more load on the engine (possibly battery) upon starting if the compressor is already in the "on" position upon starting?
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If this is a problem, the vehicle manufacturer can easily set things up so the A/C Clutch doesn't engage while the starter is engaged.
Ed
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I think the A/C system does not receive power when the ignition switch is in the Start position.
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Back when I was installing remote starters for a living, NONE of the cars I worked on received power during the crank phase. There were at least 2 hot leads for the run position. 1 for the circuits that required power during crank and 1 that was cut off when in the crank position but came back on when the ignition switch returned to the run position. Then of course the accessory wire was also dead during crank, but live when in RUN and ACC position (radio and things like that).
Some circuits are live all the time and don't go through the ignition switch like lights.
And some vehicles had a 3rd RUN lead (some GM trucks for example, and if you didn't account for them when using a remote starter the transmission would act up until the vehicle was reset).
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It didn't matter when your dad said, it and it still didn't matter.
Oh--unless your dad drove Chryslers, in which case the advice should simply have been "never turn on the AC at all".
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