A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
SM: Are you reading at the furnace? Between which two terminals?

Yes. R & W.

SM: That rules out the 24vac transformer gone bad.


C) Then I jump the two screws on the furnace control board where the
thermostat is connected (the same two I've been working with above.)
Jumping them should call for heat but the furnace doesn't start!!

SM: Were the screws on the furnace lettered? Probably R and W?

Yes.
SM: That is reasonable.

Any suggestions or corrections?

SM: Might be time to call a service company.

Not yet. Probably not ever. I have the house's original thermostat,
and I have a replacement control panel, from the same model furnace.
One of those, or both, will make it work. But I just can't believe
they both failed in the same night.

SM: Sometimes,one fails, and then "takes out" the other.


I'm trying to think of something that could account for the apparent
failure of both the stat and the control panel, but I can't.
SM: Cascade failure.


SM: Furnace usually have several things that turn it off, and one that
turns it on. That's safety for you.

They should use different names.

SM: I agree.


The second relay might not be a relay exactly. It works with the
cadmium photo cell to turn the furnace off if there is no flame in the
firebox, like if the furnace runs out of oil. And maybe if the firebox
gets too hot. I don't know. I've never had that particular problem.

SM: Can't see it from here.

Let me hold it up to the screen. Better?
SM: No, I've got the wrong glasses on.


For now, I"ll run the furnace manually 2 or 3 times a day for a couple
hours a day, or whatever it takes I was able to get the house to 79,
then turn off the furnace for at least 10 hours and it was still 64. So
I can sleep all night. I need time to think and I'll figure out what's
wrong in a day or two.

SM: I suspect you will. I'd be looking for safety
devices, and limit switches which may have been
activated.

--
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Christopher A. Young
Learn about Jesus
www.lds.org
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