One more point I don't want to be missed.
If there were an open in the resistor block, if speed number 2 didn't
work, then neither would speed number 1 (or speeds number 3 and 4,
depending on the design, although of speed number 1 is the lowest
speed, the simple design will probably always be like mine is.)
When I first diagnosed this, somehow I couldn't feel the air blowing
in speed 1, but it was.
That means it is the switch which is the problem.
And if I didn't say it already, the switch is designed so that in all
but from Off to speed 1, it makes before it breaks, which I think
would reduce to near zero the amount of sparking.
More below, continued to the end.
In alt.home.repair on Mon, 23 May 2005 04:07:50 GMT "George E.
Cawthon" posted:
meirman wrote:
((snip))
As to the heater switch, I did note during testing today that between
speeds 1, 2, 3, and 4, it makes the connection with the next speed
setting before it breaks the connection with the current one. Seems
to me this should cut down arcing to zero or near zero. Except
between off and speed one, which is the lowest speed using the least
current. Of course the design must not be as good as I'm making it
sound, or these things wouldn't be breaking all the time. (The model
from my friend's van may be the more recent one, and maybe it doesn't
fail like the old one did. Still, cars have had heater fans speed
switches since 1950 and earlier, and one would think they'd have the
bugs out by now. My car only has 76,000 miles.
Boy are you optimistic! I've had older cars most
Yes, I am. It's quite amazing at times. (And yet I can also be
cynic.)
of my life, getting them at 50,000 miles or so
(5-10 years old)and getting rid of them at over
100,000 (12-29 years old). Only recently have I
ever had a problem with a heater switch. It was a
car 9 years old with about 40,000 miles on it.
A sad commentary on car construction.
I apologize but I may not have to regrease after all, and I won't if I
don't have to because I don't want to open the switch more times than
necessary, and break the metal tabs that hold the switch together.
I tested it today with the heaviest 12 volt load I had handy today,
and that was a diaphragm-style air compressor suitable for refilling
flat tires. Nowhere near, I think, as big a load as the fan, but it
worked fine, and I couldn't even hear a difference in speed from the
other switch positions. (I wasn't using any resistors.) If I had had
10 more minutes, I could have installed the fan (if I didn't connect
the hot/cold lever) but something came up.
Glad to hear the switch is working, now to find
out if that was really the problem.
Well, I wasn't convinced it was working when I posted the above. I've
tested things before and had them work on the bench but not where they
were supposed to. And this one passed the test, minus the air
compressor, the last time.
But today I put it in, and it works. If it breaks again, I'll try to
let you guys know.
I've been repairing things since I was 7 or 8, and for the first 9
years, more than half the time, all I did was take them apart, put
them back together again, and they worked. Not only did I not know
why, I was pretty sure I didn't do anything that would make them work.
That's happened since then too. When it does, sometimes it's mystical.
It's almost like I can lay hands on the thing and it will work.
I know that I'm not the only one with this experience.
Basically that's what happened the second time I took this control
unit out. The first time I cleaned it, pushed aside the hard grease,
but this time I really did nothing. I just made a bunch of
measurements, took the switch out of the unit and put it back again,
made more measurements. (and the one test).
Meirman
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