Terry,
Not particular important, but I thought I'd mention it anyway since you
brought the subject up. I don't believe (and I'm sure other people will
disagree with me) that leaving the fan running after the engine is shut off
will help very much with the temperature rising after the engine stops.
The reason the temperature rises is heat soak - the engine is hotter than
the coolant, and since the two are in contact with each other, the heat is
transferred from the engine into the coolant.
Of course, this happens all the time when the engine is running, too.
Except that when the engine is running, the water pump moves the coolant
away from the engine into the radiator before it gets too hot. Once the
engine has stopped, there is no movement of the coolant (except a very
small amount due to convection) so it just sits in the block getting hotter
and hotter.
The reason I say that the fan won't help much is because the fan cools the
coolant in the radiator - *not* the coolant in the block. And when the
engine is not running, the water pump is not turning, so it's the coolant
in the block which is heating up, not the coolant in the radiator.
Of course, if you're happy with the way your car is wired, that's fine.
But my fan is wired through my ignition switch (by a PO, not by me), and
I'm quite happy with that.
As always, any thoughts from people who know more about this than I do are
welcome!
Dean
--------------
Date: Tue, 3 Apr 2001 18:28:48 -0700 (PDT)
From: Terry Thompson <firespiter@yahoo.com>
Subject: Re: Switched power for fan
<snip>
And also the
temperature seems to increase when you let the car sit
for a few minutes (pressure cooker affect?). When you
run into the store for five or ten minutes, it's
actually hotter than when you got there. So I like
having a fan that runs for a while after I get out to
drop the radiator temp.
- -Terry
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