On Tue, 10 Dec 2013 19:43:29 +0000, Danny D'Amico wrote:
I was hoping to just debug the (much simpler?) thermostat first, but,
since someone asked about the furnace, I went down there and noticed
the door was off.
When I put the door back, the blower just blew incessantly.
So I took the door back off, and pressed the white switch that gets
pressed when the blower door is on, and the blower just kept blowing
for as long as I held the switch pushed in.
Back upstairs, teh cover is still off the thermostat, so the thermostat
settings are still at HEAT (versus OFF, COOL) and AUTO (versus FAN ON).
This is the schematic printed on the inside of the door panel:
This is another smaller schematic above that big one on the door panel:
And, this is on the outside of the door, for the electric pilot:
What I'll do right now is read up on the net for how this furnace
works, and the first thing I'll do is try to identify the parts.
Close the cover. And shut the power off to the furnace for 5 mins or so
and turn on the power. What happens now? Still fan comes on? Then we'll
do next step. Usually when hi temp limit switch(fixed temp. thermostat)
triggers furnace flame shuts off and fan runs to cool and when that
switch opens, fan will stop. I don't think your furnace is hot now.
Just maybe thatr switch is stuck close.(this is just one of possible
If this is the case furnace will lock up 2 hours something like that.
By turning power on/off you can defeat that 2 hour wait to try again.
Is it cold there? It is -14C and light snow here today.
On Tue, 10 Dec 2013 13:31:33 -0700, Tony Hwang wrote:
I am in warm clothes, but it's going to be around freezing
in Silicon Valley tonight, so, for *us*, that's coooold!
Yes, I know, that's warm for most of you!
Anyway, I'm reading all the suggestions, and lining up my
ducks, as I am first and foremost trying to figure out how
the darn thing is *supposed* to work.
So, for that, I had to first identify the parts, which,
for the most part, I think I have now.
So, now it's time to try to figure out how the thing is
supposed to work.
And then on to the debugging steps.
I'll report back, as it's getting dark and colder outside
as I type ...
On Tue, 10 Dec 2013 13:31:33 -0700, Tony Hwang wrote:
Something I did must have worked, at least temporarily, because I got
pilot light finally tonight:
And then I got main burner:
And then I got blower:
But, I accidentally loosened the tape holding the door switch in,
so the whole thing died.
Trying again and again, I was able to get it to restart a couple of
times, but it shuts off almost immediately - like after just a minute
or two - so I have to figure out what's turning it off ...
How did that happen? Who left your furnace open and why?
Ok, you've got electricity to the furnace. No blown fuses etc.
At this point the fan should not be on.
Read section IV of the manual. It explains what should occur and when in
the heating process.
Confirm that you have gas.
Find the furnace switch in your breaker box. Turn it off. Give it a few
minutes. Turn it back on
On Tuesday, December 10, 2013 4:12:10 PM UTC-5, David L. Martel wrote:
That's a good question. Did it come off at some point in the
diagnostic process or was it off to begin with and the cause
of the whole problem?
The fan is probably on because he's been screwing around with the
thermostat and now has something screwed up there.
With a simple old mercury thermostat like that, there isn't
much to fail. I've never seen one that just stopped working.
On Tue, 10 Dec 2013 15:15:00 -0800, firstname.lastname@example.org wrote:
IIRC, I took it off months ago, when it was something like 95 degrees
outside, but all I could do was stare at the setup as I didn't
understand how to troubleshoot.
But, not having A/C in 95 degree weather is nothing like not having
heat in 32 degree weather; so, it's more important to figure it out
now than in the summer.
I'm ok, by the way; but the wife and kids don't like the cold.
The fact that I assume 120 volts (and whatever the high-tension leads
have in them) is there, is the key reason why I'm not just jumping
leads just yet.
I want to *measure* first. That's not dangerous. Jumping things is
much more dangerous (if I make a mistake).
So, at the moment, I concentrated first on identifying all the parts
of the furnace (which I snapped a picture of and posted separately).
Then, I am concentrating on figuring out how those parts play together.
After that, I'll do the measuring.
And then the jumping.
I'm sorry I'm probably way slower than you guys would like, but, I'm
trying to actually understand the darn thing first ... Thanks for
your patience. I've still got to read that Carrier manual ...
Jumping is involved with 24V AC control voltage. Not dangerous.
Let me ask you, can you read schematics? Can you id. parts in the
furnace like piezo ignitor, limit switches(some are NO, some are NC),
do you understand relay logic? First thing I suggested you was to reset
the furnace by powering it off/on. Gently tap all the relays you can
see. Am\nother issue may be you may have messed up the 'stat when you
open it and reassembled. We're going around same routine when you had
alarm trouble wating lot of time.
Start with the basics:
1) You have determined that the furnace has power. That's good.
2) Turn the thermostat down below the temperature of the house...
Have an assistant stand by the thermostat and now go to the furnace.
When you are there have them turn the thermostat up.
Does anything at all happen?
Of so...describe what it is doing and post back.
If *absolutely* nothing happens, then a wire on the thermostat could be
If you hear a click and gas starts to flow, but nothing ignites, then it
shuts down...then the igniter is bad.
Then there is no reason blower would run. Just jumper W and C at the
furnace after taping down the cover interlock switch. If furnace works
go to 'stat and do the ssame. If furnace does not start then can assue
wire is broken or loose some where.
He already determined that the blower came on. Now, we need to determine
why. That is why I asked for him to get the t-stat set up to all off, then
have the cover replaced. If the blower turns back on something is making
an improper contact, one of the relays is stuck, or the HTR relay is not
functional (bad coil). That is if he is correct when he stated that he had
a nominal control voltage. 27vac, I believe.
Be careful asking him to play with the access door switch. That switch has
120V going to it. Sometimes they are not finger proof. :-)
I already mentioned about that too. Maybe he can read but can't
comprehend? Getting zapped will make him call for pro help. It is hard
to get killed by 120V AC unless one's feet are bare and wet. If he is
afraid, some one has to be nearby to watch, ready to throw the breaker
in case he is getting zapped. Desire to learn is good thing but one has
to have some basic knowledge first. He can enroll at community college
to take electricity 101 or some thing like that. Oh, no, then he'll be
more dangerous knowing little bit......
Check for 24VAC between SEC1 and SEC 2. If there is no 24VAC, check the
transformer solder joints on the circuit board
Leave one lead on SEC2 and check for 24VAC on the red wire terminal. If you
have 24VAC the interlocks are OK. If not, trace back until the open
interlock is found
With the stat calling for heat, check for 24VAC at the W terminal. If you
have 24VAC, the stat heat circuit is good. You should hear the gas valve
click and the igniter spark.
If you look at the schematic for 394JA you will see the blower motor relay
is normally closed. If the furnace is powered up and there is not 24VAC at
the R terminal, the blower motor will run right away and not shut off, which
is what you said it's doing (note the jumper between R and GH)
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.