On Tue, 11 Feb 2014 19:13:52 -0500, Stormin Mormon
And by the way, the stuff I had for salting sidewalks that turned into a
glob was calcium chloride, like you thought.
Very different from my 50 pound bag of CaCl2, which never turned into a
glob (though I had it less than a year, not 10 or 15 like this) , and
which had a big puddle of water at the bottom and on the other side of
the separator,( not like this which had no water, but was in a capped
container, but otoh, has cracks in the container from age. I should
With your help, I've made a lot of progress on the furnace, but I have a
paradox, I think.
All of these steps done when the house was cold again.
A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
them. That alone means that the thermostatic switch in the thermostat
is open, or the voltage drop would be very close to zero.
B) But to be sure, I disconnected one of the wires to the themostat,
measured the voltage between that wire and the other wire/screw (not
disconnected), and it was zero of course. Measured the resistance it
was over 100,000 ohms. Confirmation.
OKay, so an open switch means the thermostat is not calling for heat,
even when it is cold in the house.
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!!
A and B indicate a bad thermostat. C indicates a bad furnace.
Specifally, a bad furnace control board because other tests have
excluded everything else.
I just don't believe they both failed the same night.
BTW, the furnace control board only has 2 resistors, 1 ceramic disc
capacitor, 2 transistors, and 2 relays***.
Any suggestions or corrections?
***I have found in the "schematic" the black relay whose armature I've
pushed to start the furnace. It is labeled "limit switch" and it
interrupts the 110 volts to the whole control board and the motors and
ignition transformer. But the wiring "diagram" on the same page for my
model shows another limit switch in the fan and limit control, a
separate box that extends iiuc into the firebox. No wonder I'm
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.
\> All of these steps done when the house was cold again.
Yes, the thermostat is open. What is the setting of the thermostat?
Should it be open or closed? Set the temp to 50 and it should be open,
unless your house is really cold. Set it to 85 and it should be closed.
What? You have 24v across the wires when they are connected to the
thermostat but not when they are disconnected from the thermostat? This
makes no sense to me.
Measured the resistance it
You've lost me. What are you confirming? Are you measuring the resistance
across the thermostat? Is the thermostat open or closed? Set the thermostat
really hot (80 or 90). Be sure that the stat is set for heat That should
close the switch. You should get a very low resistance
Yes, if the thermostat is open it is not calling for heat. Look you
aren't being very clear. Should the thermostat be calling for heat? Please
tell us the temp setting for the thermostat and confirm that the stat is set
Is there 24v across these wires before they are connected?
On Tue, 11 Feb 2014 20:14:03 -0500, "David L. Martel"
I'm sorry. The furnace, not the thermostat. No voltage between the
thermostat wires when one wire is disconnected from the *furnace*, not
the thermostat, I'm standing at the furnace and disconnecting the wire
there. . The thermostat itself is where it's always been, but it is
almost inaccessible right now, since I hurt my back.
That the thermostat switch is open.
Yes. One wire, red still screwed to the furnace control board and one
wire, white, unscrewed from it. Plus I checked which screws get the
thermostat wires, and those are it.
It should have been closed then because the house was cold at the time,
maybe 58 degrees when the stat is set at 68 and normally keeps the house
But when I measure the resistance between the two wires from the
thermostat, it is over 100,000 ohms. It's not closed when it should be
Well I can't reset the thermostat until I get access. Requires some
heavy lifting. Probably need a friend.
Set at 68 and set to call for heat. I havent changed that in years.
(The AC is broken and during the late-spring, summer, early fall I just
turn off the power to the furnace, so it doesn't start on a cold night.)
There was a couple minutes earlier, when I did test 1, And I measure
it earlier too and also got 24v. So a jumper from one screw to
another should start the furnace. But it doesn't start.
Sorry I was confusing.
On Tuesday, February 11, 2014 6:52:50 PM UTC-5, micky wrote:
Assuming you're on the right wires, I agree.
Again, if you're indeed on the wires that go to the
thermostat, then either there is a break in the wiring
or the thermostat is bad.
You have 24V at the two contacts at the furnace that go
to the thermostat. Should be the red and white wires.
When you connect them together and the furnace doesn't start,
did you measure the output of the transformer? 24V there?
You could have a bad connection there in the furnace wiring.
If a connection was high resistance, you could see 24V
at the terminals, but when you connect them together,
enough current would not flow to close the relay.
Imagine the circuit being correctly working, but then
a 10K resistor is put in series (simulating the bad connection)
You'd still see 24V open circuit, but if you connect
the terminals not enough current will flow to close the
relay. Could also be some bad component too, eg the
relay coil, presenting a higher resistance than should
The other part, about the thermostat and/or wires going
to it, no more ideas on what's going on there.
On Wed, 12 Feb 2014 07:37:30 -0800 (PST), " email@example.com"
Definitely the right wires.
FWIW, the handles on two of my toilets failed within 3 months of each
other, after 34 years. I have to check the third toilet, that I don't
use. But that's still not the same night.
I measured it with no load. You're right, I should measure again with a
A lot of the places I'd like to take measurements from are not
available. The circuit board is in a metal box, a half inch about the
I have insulation piercing alligator clips, for testing. Maybe I'll try
those. (In high school I had to use an ice pick, but it was only 12
Not sure whether to just change control boxes or to try to debug this
I'm going to go eat lunch. Seems like a reasonable compromise.
A couple Sundays ago, at church we had a furnace
go down. Cold in that section of the building.
It had given trouble several times, and this
time they called in an outside company to look
at it. Sure enough, one of the safety switches
was just a bit out of place, and wasn't getting
activated like it ought have.
On Wednesday, February 12, 2014 11:27:00 AM UTC-5, Stormin Mormon wrote:
Since pressing that started the furnace and kept it going,
it would seem to me
that either some sensor is telling the control board to shut down
or the control board is bad. A faulty flame sensor would be
a prime culprit.
The other part, where he's saying the thermostat wires at the
furnace indicate an open, don't know what to say about that.
Operator error perhaps?
On Wed, 12 Feb 2014 08:44:35 -0800 (PST), " firstname.lastname@example.org"
Very good idea. I've been ignoring the flame sensor, except to note
how it's connected on the schematic.
I can disconnect one lead and test if it's bad or not. It conducts
when light is sensed, I red. Cadmium sulfite "The resistance value
of an LDR becomes smaller, as the LDR is more and more exposed. The
material is usually cadmium sulfide, the dark resistance is 1.10 M ohm
resistor while the light resistance is about 75-300 ohm. LDR's have a
relatively slow response time." I"m sure disconnecting will still work,
though the Carrier diagram gives no explanation for the "flame detection
electronic network." It's just a "black box". Even t hough it's made
of clear plastic, I still have no idea how it works.
They're only $14 on Amazon, with lots of brackets, plus $5 shipping,
but I have a spare one fo them too.
On Wed, 12 Feb 2014 11:27:00 -0500, Stormin Mormon
Yes. R & W.
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.
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.
They should use different names.
Let me hold it up to the screen. Better?
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.
On Wednesday, February 12, 2014 12:02:07 PM UTC-5, micky wrote:
Maybe we should recap where you're at.
A - You say with the thermostat wires disconnected at the furnace,
you can connect a meter to those wires going back to the
thermostat and measure an open circuit, even
though it's cold and the thermostat should be calling for heat.
That's across the red and white wires, which were
connected to the R and W terminals, before you removed them.
Have you verified this? It's repeatable? You're sure the
meter is on the ohm or continuity setting? How many wires
go to the thermostat? 3? heat, fan, power? If you're
100% sure about this, then there is a problem with the
thermostat or the wiring going to it.
It's also a little weird that you said something about not
being able to get to the thermostat without moving furniture?
That limits the ability to diagnose.
B - You say that shorting the R and W terminals, the furnace
C - You can get the furnace to fire up and run by holding
down that relay button. It's not clear, is that with the thermostat
wires disconnected and the terminals open? From the description
it sounds like that is some kind of limit relay, but it
seems odd to me that it would make the furnace start up by
pushing it, if there is no call for heat. Any relay, etc
I've seen that was marked as "limit" could cut it off if
something wasn't right, but would not make it fire if there
was no call for heat.
Have you looked at the flame sensor? Not dirty? With a
furnace like that I'd have spare nozzle, flame sensor, filter,
etc, ie the common cheap things that can go wrong.
Also, with years of experience with that furnace, I would
think you'd know what gets tripped by what, at least to
some extent. For example, if it starts up, no flame is
detected, it shuts down. What do you have to push to reset
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