I'm having trouble with my 20+ year-old Sears 867.762340 gas furnace.
About once a month, it will fail to ignite the burners. It just sits there
with the vent blower running.
If I short out the contacts on the pressure switch, the burners start right
up and everything works normally.
I've dismantled the relevant parts. Checked the gas vent from top and
bottom; cleaned the rubber sensor tubes and checked them for leaks; cleaned
the insides of the metal fittings to which they attach; checked the
electrical connections to the pressure switch; and checked the pressure
switch itself (it responds immediately to very light sucking and blowing on
its input ports). Everything was squeaky clean as far as I could tell, and
I didn't find anything wrong with any of the components.
After re-assembly, the old behavior is back. Furnace fails to start about
once a month.
The only thing I can think of is that the switch contacts inside the
pressure switch are worn or corroded, so they don't always close the
Before I sink $70 into a new pressure switch, does anyone have any ideas
about what might else be causing this problem? And are the pressure
switches known to wear out?
Your help greatly appreciated.
Oh, the ol 867.******. That one was a real sum biatch to work on.
Just plan on taking a day off once a month and go away.
Then leave the short in place. It sounds like you've already figured
but did you check in between?
So was this a thorough cleaning with soap and water with an air drying
or did you just give it a once around the horn?
Eww, that could be a problem. THe insides of the fittings have an
exacting tolerance. You could have really screwed something up there.
Did they look like spade terminals or bath tub play toys?
Oh my! Do you write for Hustler in your spare time?
Go out of town that day of the month
Well, some are good thinkers......others are not. Where would you be?
Perssure switches never never never ever wear out.
I would start replacing parts one at a time from the cheapest part and
gradually work up to the the more expensive parts. This is a sure way
of getting it repaired right.
No problem. Dont thank me. I do this as a public service. You can ask
me anytime. I would replace your thermostat first though. After all,
its almost always the thermostat.
On Sat, 05 Jan 2008 08:56:59 -0600, The Freon Cowboy wrote:
Interesting suggestion! It was quite windy when it failed yesterday, and
normally we don't get much.
However, the winds were gusty and intermittent. Wouldn't you expect the
furnace to start as soon as the pressure in the vent was OK? What happens
is that the furnace sits with the vent blower running, and it would stay
that way forever if I didn't do something.
condensation in the air tube.. Take it/them off and blow the itty bitty
moisture out and things will be fine.. Dew point cause that. No real
cure. Only happens in certain circumstances. Be sure there are no traps
in the line.(low points)
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