>Today's cold weather, -2F as I was driving in (Canadians: Yes, I know this
>is a warm day for you.), has brought forth one of the old cold starting
>myths. This alleged hint says that you should turn on your headlights for
a
>few seconds before trying to start your car. I work in a building just
full
>of engineers, and most everybody's got an opinion. The comments on this
>range from "GARBAGE!!" (>50%) to various thoughts about warming the
>electrolyte, warming the battery terminals, etc.
>
>Most of us wonder how a few seconds of a few amps is going to do more of
>whatever the effect is supposed to be, than the first few milliseconds of
>starter current. Does anyone have more info on this, what effect is
>supposed to be, etc.?
>
>Stu
>
Here's my musings on the myth:
Since battery capacity decreases with ambient temperature, I'd suspect that
people who subscribe to this method probably are pretty well acquainted with
their jumper cables and the location of the battery in their neighbor's
cars.
You're right, compared to the current drawn by the starter, the 20 or so
amps of the lighting circuit would create insignificant heating of the
electrolyte, terminals, etc.
What I have seen the lights on method work for is corroded battery
connections. I think the resistance of the corrosion is such that it won't
allow the starter to engage, but will run the accessories due to their lower
current demand. I think what happens is pulling a few amps through the
corroded connection burns some of the crap off, allowing the connection to
pass the higher current of the starter. I had this happen to me a couple of
years ago, cleaned the contacts and haven't had any trouble since.
IMHO, the only real solution for cold starting problems is to maintain the
vehicle properly. I've been stuck maybe a handful of times in 20+ years of
driving in the Detroit area, and it was always because of something I
neglected to take care of... battery, terminals, cables, plugs, points, etc.
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