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 ?

 

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.

 

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".

 

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

 

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

 

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.

 

Except if your filter is damp enough to get moldy itself -- as happened to
the filter in my '01 Odyssey a few years ago, after I had gone through the
hassle (and it is a hassle with that year model) and expense of changing the
filter only a couple of months before. Now I try to dry out the system a
little before I turn it off, but it's not easy to do in Houston in the
summer.



--- news://freenews.netfront.net/ - complaints: ---

 

Doesn't it place more load on the engine (possibly battery) upon
starting if the compressor is already in the "on" position upon
starting?

 

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

 

I think the A/C system does not receive power when the ignition switch is
in the Start position.

 

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).