On Wed, 11 Dec 2013 00:26:39 +0000, Danny D'Amico wrote:
I apologize for not having looked far enough into the
mouse-infested recesses of the ductwork to provide the
There is no power switch; but, there is a power cord,
which is plugged directly into a wall outlet, *behind*
the furnace (and to the side):
I made the mistake today of unplugging it, and then
regretted that since I had to get covered in insulation
and mouse poop in order to plug it back in.
Next time, I'll just hit the circuit breaker!
You're testing the wrong things. The thermostat is very unlikely to fail.
Please put the thermostat back together. Now slide the fan button to "on".
Does the fan come on? This will tell you whether there is electricity going
to the furnace (?). What sort of heater are we talking about?
On Tue, 10 Dec 2013 13:43:19 -0500, David L. Martel wrote:
I don't know anything about heating systems; so, I was planning on debugging
from the thermostat to the furnace.
The furnace is a Payne 394JAW, built in 1988.
I called Carrier this morning (800-227-7437x4) and asked for a troubleshooting
guide and parts list. They said I had to go to a local dealer, but, they did
send me a document named: 40394dp65-a.pdf, and titled:
Bryant, day night, Payne 394J, Series B, Sizes 030 thru 095, 40394DP6-A 10/15/87
installation, operation, and maintenance instructions
Upflow Gas-Fired, Natural-Draft Furnace, 9 pages
For use in California only
BTW, where can I post this PDF so you (and others) can see it, as I couldn't
find anything on the web for how to troubleshoot the furnace itself, and the
four companies that Carrier told me to call all told me to take a hike (in
effect). They don't deal with residential consumers, at least not for PDFs
and parts orders.
NOTE: I'll see if I can convert the PDF to JPG so I can post it for you...
I'll head on down to the furnace after checking the thermostat; but,
I'm tending to agree with you, that the thermostat looks too simple
to be the problem...
*Based on past experiences with customers, two things I suggest that you
check. Make sure that the disconnect switch for the furnace is on, and make
sure that the service door on the furnace is closed correctly. If the
service door is not closed properly the furnace will not run.
Your furnace will have terminals marked on the boards; C, W, G, Y(if AC
is present. C is common lead for control power, 24V AC), W is heat lead,
G is fan lead, Y is compressor lead. If you jumper C and W heat with
come on and after some delay fan will start. If you jumper C and G fan
will run. Make ssure the furnace cover interlock switch is cheated with
a piece of tape.(this switch breaks power to the furnace when open)
You can do this jumper test from thermostat terminals too. Do you have
multi meter? Know how to it and read schematics? Fiurnace is just
simple one line logic sequence......
So, page eight or nine had trouble shooting. I hope
Danny did those checks.
I tried download the PDF, but the file came through
corrupted. What I was able to see of the PNG, there
is very little troubleshooting information provided.
And precious little about the furnace.
On Tue, 10 Dec 2013 17:02:14 -0500, Stormin Mormon wrote:
I googled for the name of the document that Carrier sent me:
This directory came up; which contains a *lot* of furnace PDFs:
This one looks to be similar (it's for the 394J where mine is 394JAW):
This one has an even closer model number (394JAZ where mine is 394JAW):
On Tue, 10 Dec 2013 18:06:51 -0500, Stormin Mormon wrote:
Thanks. I just printed that manual and haven't tried
that troubleshooting yet. It took all this time to
learn how to identify what was there, and I think,
for the most part, I've figured out what most of the
I'm not yet sure what this thing is (a sensor?):
Nor, am I sure why this thing called a Lockout Timer exists:
So, I'm taking in the data, bit by bit and will get to the
troubleshooting guide from Carrier.
1st: Remove furnace access door (effectively cuts off control power).
2nd: Put thermostat back together making sure that all switches are in
the -off- position, and turn the temperature select to its lowest
3rd: Replace furnace door.
Does the blower immediately turn on still?
If no: Switch thermostat to -heat- and set to highest temperature. Go
back to the furnace and listen. The blower should be running and
in a minute, or so, the burner should kick on. This unit might have
a delay for the blower, so wait 2 minutes before deciding that things
are not functioning. That is it for this part until you come back with
If Yes: Either the heating or the cooling relay is sticking. Once again, get back
with an answer.
Anyway, download above link. If it is corrupted, update your PDF reader.
On Tue, 10 Dec 2013 18:19:44 -0600, Irreverent Maximus wrote:
I read the entire PDF, from front to back.
Here's a summary of what I gleaned about the furnace operation:
1. Red wire is 24VAC hot.
2. Thermostat "calls for heat" by connecting Red to White.
3. Thermostat "calls for fan" by connecting Red to Green.
Thermostat "calls for heating" by connecting Red to White.
Power then goes from the Transformer -> Fusible Link -> Limit Switch ->
Vent Safety Shut-off Switch -> pilot (both "pick" & "hold" gas valves)
such that pilot gas flows, where it ignites.
~60 seconds after pilot, safety pilot switches its contacts and energizes
the main valve portion of the gas valve, where, about 10 seconds later,
the main gas valve opens, and the main gas is ignited by the pilot flame.
~75 seconds after the pilot lights, the fan control board activates the
fan on low speed (it uses the low speed for heating purposes).
When the thermostat "is satisfied", the connection between R & W is broken.
Gas is immediately stopped to both the pilot and main burners.
The blower continues for about 100 seconds.
If the furnace overheats, the Limit Switch opens.
If the furnace overheats in the vestibule, the Fusible Link opens.
If the furnace overheats in the vents, the Vent Safety Switch opens.
I see the fusible link on the red wire here:
I'm guessing this is the limit switch:
But, I can't seem to find the "Vent Safety Switch".
Yep, that's a limit but look to see if there's a little push button
reset between the 1/4" Faston terminals where the wires plug on to the
switch. Some of them have a manual reset that will click when it is
pushed in to reset it. ^_^
When that trips, it's in series with all the other safeties and will cut
the 24vac control voltage to the furnace. If it isn't an automatic
reset, you have to find the little buttons and push them in to reset
the control circuit. Like a circuit breaker, it tripped for a reason
so you need to investigate the cause. This is where experience comes
into play. Perhaps a friendly service tech will show you what's wrong
and answer questions about it. I had a little old lady crawl under her
house with me so I could show her what was wrong with her furnace and
what needed to be done to repair it. ^_^
That is located inside the flue. You took a pic. of it. Sqare bakelite
lo0king thing with two wires mounted on the flue. The sensor is inserted
into flue to detect vent gas temp. This is one of couple safety thing
when triggered furnace will shut down pronto and lockout timer starts.
You can't see the lockout timer counting pulse w/o 'scope.
On Tue, 10 Dec 2013 23:08:39 -0700, Tony Hwang wrote:
I see it. Thanks. This is the backside of the thing:
So that makes four safety switches to debug next time:
1. The fusible link (also visible in that picture above)
2. The vent safety shutoff switch (also in that picture above)
3. The lockout timer (also in that picture above)
4. The limit switch (visible in the picture below)
The only one of those four that I don't understand is the
lockout timer. Googling for the part number 990-141-1, I find
it's a $200 24VAC 60HZ SPST switch:
This PDF purports to explain what it does:
It seems to have a "pickup time" of 7 seconds, and a "dropout time"
of 5 minutes.
Since it's hooked in series with the pilot light and spark igniter,
it has something do do with stopping that circuitry after about
five minutes. But, I'm not sure what controls it, unless it's a
Is that what it is? A timer to interrupt current to the pilot
switch after five minutes?
The small cylindrical thing with a red tip on one of the wires is a "one
shot" thermal fuse and if temps get too high it will pop. It's in series
with all the other safeties and will kill the control voltage. ^_^
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