How to test a wall thermostat to see if it's actually working?

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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 answer sooner...
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):
http://farm6.staticflickr.com/5477/11327971174_cd6604d692_o.gif
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!
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Danny,
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?
Dave M.
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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 Cancels 40394DP61-A
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...
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On Tue, 10 Dec 2013 19:17:47 +0000 (UTC), Danny D'Amico

Just upload it here and you will get a URL you can post in a text message.
http://en.packupload.com/
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On Tue, 10 Dec 2013 14:20:34 -0500, Metspitzer wrote:

OK. Here is the 9-page Payne 394 JAW PDF that Carrier sent me today: http://en.packupload.com/085CHEN6AJG
I had also just finished converting it to PNG for upload to Flickr: P1:
http://farm6.staticflickr.com/5477/11312392545_68039c1493_o.png
P2:
http://farm6.staticflickr.com/5515/11312392055_63819ab272_o.png
P3:
http://farm4.staticflickr.com/3782/11312391895_d409270195_o.png
P4:
http://farm6.staticflickr.com/5524/11312436916_db792398ca_o.png
P5:
http://farm6.staticflickr.com/5488/11312391565_a0c0dfefb3_o.png
P6:
http://farm3.staticflickr.com/2889/11312511713_0e1f5f9aa7_o.png
P7:
http://farm6.staticflickr.com/5496/11312436006_debe96421a_o.png
P8:
http://farm3.staticflickr.com/2892/11312511233_936c147a7b_o.png
P9:
http://farm8.staticflickr.com/7372/11312435476_d1cdbe4107_o.png
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...
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*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.
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John Grabowski wrote:

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......
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On 12/10/2013 3:04 PM, John Grabowski wrote:

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.
--
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Christopher A. Young
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On Tue, 10 Dec 2013 17:02:14 -0500, Stormin Mormon wrote:

I googled for the name of the document that Carrier sent me: 40394dp65-a.pdf
This directory came up; which contains a *lot* of furnace PDFs: http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/
This one looks to be similar (it's for the 394J where mine is 394JAW): http://xpedio.carrier.com/idc/groups/public/documents/techlit/40394dp65-a.pdf
This one has an even closer model number (394JAZ where mine is 394JAW): http://xpedio.carrier.com/idc/groups/public/documents/techlit/ii394j-30-1.pdf
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On 12/10/2013 5:51 PM, Danny D'Amico wrote:

not much useful information to be had. There was some troubleshooting, which I hope you read and tried.
Writtenly lookingish set not appearingly to be Chingrisher.
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Christopher A. Young
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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 things do.
I'm not yet sure what this thing is (a sensor?):
http://farm3.staticflickr.com/2814/11315574703_f10de1c8bd_o.gif
Nor, am I sure why this thing called a Lockout Timer exists:
http://farm8.staticflickr.com/7323/11315342803_5356224304_o.gif
So, I'm taking in the data, bit by bit and will get to the troubleshooting guide from Carrier.
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http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/40394dp65-a.pdf
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 setting.
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 an answer.
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.
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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:
Summary: 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.
Details: 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:
http://farm8.staticflickr.com/7323/11315342803_5356224304_o.gif
I'm guessing this is the limit switch:
http://farm3.staticflickr.com/2814/11315574703_f10de1c8bd_o.gif
But, I can't seem to find the "Vent Safety Switch".
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On 12/10/2013 10:00 PM, Danny D'Amico wrote:

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. ^_^
TDD
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On Tue, 10 Dec 2013 22:14:03 -0600, The Daring Dufas wrote:

I found this picture on the net of the little red push button:
http://www.justanswer.com/uploads/OutbackHVAC/2009-04-29_192852_limit_-_manual_reset.jpg
So now that I know what to look for, I can see that same button in my limit switch, only mine is black:
http://farm8.staticflickr.com/7371/11319102156_2490f0e3a7_o.gif
Now the only safety switch I haven't found is the VSSS Vent safety shutoff switch.
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On 12/10/2013 11:27 PM, Danny D'Amico wrote:

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. ^_^
TDD
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Danny D'Amico wrote:

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.
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On Tue, 10 Dec 2013 23:08:39 -0700, Tony Hwang wrote:

I see it. Thanks. This is the backside of the thing:
http://farm8.staticflickr.com/7323/11315342803_5356224304_o.gif
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)
http://farm3.staticflickr.com/2814/11315574703_f10de1c8bd_o.gif
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: http://technicalhotandcoldparts.com/carrier-hh72ch003-lockout-timer-control.html
This PDF purports to explain what it does: http://www.lennoxproducts.com/wp-content/uploads/2012/05/HH72CH003.pdf
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 pure timer.
Is that what it is? A timer to interrupt current to the pilot switch after five minutes?
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On Wed, 11 Dec 2013 05:27:17 +0000, Danny D'Amico wrote:

After googling for a while, I think the reason I can't see the VSSS is because it's *inside* the plenum!
I think it's attached to the brown board, like this from the net:
http://www.justanswer.com/uploads/OutbackHVAC/2009-04-29_222314_high_limit.jpg
So, the VSSS would then be on the other side of *this* brown board:
http://farm8.staticflickr.com/7323/11315342803_5356224304_o.gif
Is that correct?
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On 12/10/2013 11:32 PM, Danny D'Amico wrote:

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. ^_^
TDD
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