"Bruce" wrote in message
7.136...
Bruce wrote in
7.136:

I've got a 9 year old natural gas York downflow furnace, with a
set-back thermostat. I don't have the capacity in front of me, but it
heats a 5 bedroom house.

It's been working just fine, until a few months ago. When the
thermostat calls for heat, sometimes it won't go on. Nothing. If I
take off the blower cover panel, and press and hold in the momentary
blower lockout switch, it will go on. When I release the switch, it
goes off, as it should, since this switch is inteded to turn the
furnace off when the blower cover panel is removed. I then put the
panel back on, which depress and holds in the switch (as long as the
panel is on - which is during normal use), and the furnace goes on
fine and heats the house to the set tempeerature.

When the house tempereature drops below the set point, and the
thermostat calls for heat, 'usually' the furnace goes on. But, when
it doesn't, I repeat the steps above, and it's comes back on.
Sometimes it'll go for a week without any failures, but sometimes it
will fail many times in a row.

I jumped the thermostat, and tried a new thermostat, and have
determined this is not the problem.

To take the blower lockout switch out of the equation, I installed a
new one, and wired it for always closed, but the same problem occurs.
If I push and release (sometimes it has to be done repeatedly during a
failure) the switch, opening and closing the circuit, the furnace will
come on. It will always come on; sometimes one push, sometimes many.

I had a repairman out (very reputable company), and he suspected the
control module. A new module was ordered, and a week later another
fellow brought it out to install it, only to find it was the wrong
part. Not all bad though, because this fellow isn't all that sure
that the control module is the problem. He jumped the thermostat at
the control module, and every time he jumped it there, the furnace
came on. He thinks maybe a gas control valve, but says that the first
repairman should be able to nail down the problem. Is this true, or
is this a 'replace parts until it's fixed' job?

One more bit of info: I don't remember for certain, but when the first
repairman was out, I do think there was one or two times when he
jumped the thermostat at the control module and the furnace didn't
come on.

The next time the furnace doesn't come on (tonight), I am going to
jump the thermostat at the control module and see if it does come on.

What really has got me stumped is that when it fails, one or more
pushes on the (new or old) blower lockout switch will make it work.
Everytime.

Any ideas?

Ok. It failed. I removed the wall thermostat, and jumped it at the
control module. The furnace didn't go on. While still jumped, I pushed
the blower lockout switch in and out a few times, and the furnace came
on.

Bubba, the diagnostic light does not blink when a failure occurs. It
does have the blink codes shown on the side of the furnace, should I need
those. However, it does blink once each time the blower lockout switch
is pressed. I assume this is simply due to the reset.

HvacTech2, thanks for your reply. Yes, I certainly hope they can
diagnose rather than replace parts until it works, but I'm alread into
them for the initial visit at $95. Perhaps I should cut my losses and
get another company.

Thanks all,
Bruce

This is Turtle.

Bruce your in Parts changing mode already . You might cut your loses and call a
recommended service company to look at it.

TURTLE