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

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He definitely needs to slow down a bit and wait for a few more TSR tips to show up.
Trouble shooting starts with the basics, not what one suspects unless the symptoms are a known, recurring event. By setting up the system for a normal start sequence, and waiting the appropriate amount of time, all of the issues with the T-stat would not have been.
If the system was reset and things were started over again I would wager that the unit would work again. This time, do the test with the cover in place. Check for normal operation, first, then find out why things are not working. Find the path of electricity (hence, the logic of the circuit), and follow it until the path stops. Just bumping the interlock would not cause any of the other safeties to engage, and would restart the start up sequence.
Just as with physics, observation with repeatable results is necessary to figure out what is going wrong. As for his AC, I wonder if there is a blown fuse out in the fusible disconnect outside.
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On Wed, 11 Dec 2013 11:49:18 -0600, Irreverent Maximus wrote:

This morning, I pulled the plug, and then, one by one, disconnected *every* wire I could, and cleaned the contact surfaces, and reconnected them.
I also blew compressed air over the boards, and tapped on each solenoid of the gas valve and relays in the fan-control PCB.
This took about an hour. When I powered it back up, I heard a click click click, and then a small whoosh, and then after a while, a bigger whoosh, and finally the blower.
The house is toasty right now - but it has only been working for a couple of hours. Thanks for all the help & advice!
http://farm8.staticflickr.com/7370/11327883015_a59b2434e2_o.gif
I'll report back, to let you know how it progresses along over the next day or three ...
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On 12/11/2013 12:33 PM, snipped-for-privacy@optonline.net wrote:

In one of the Scott Adams "Dilbert" books, he tells of a company that called a copier repairman. The engineers had dissembled (dismembered) the machine, and written notebooks of theories on why it wasn't working. The problem was someone put toner in the imager container. Normally a half hour diagnosis and fix. To reassemble the copier and reset all the timing gears took several days.
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On Wed, 11 Dec 2013 13:12:37 -0500, Stormin Mormon wrote:

A *lot* of things get fixed, simply by throwing parts at the problem. Nothing wrong with that. Sometimes the person throwing the parts actually knows what they're doing; sometimes not.
Take the oft-cited case of vibration when braking? Must be "warp", right? The rotors must be warped like a potato chip. Solution? Replace (or turn) the rotors. Right? Everyone knows this, right?
When *I* had vibration while braking, I tried to measure this so-called "warp". You can't measure it on the car (that would be runout), so, I measured it off the car. Hmmmm.... there was no warp. Huh?
Turns out, for normal people (not racing braking systems), warp just doesn't really happen. While a ton of suspension components can cause vibration at various speeds, the classic brake-related vibration at speed is caused, usually, by disk thickness variation caused, most often, by braking deposits, building up over time.
The solution, once you *understand* that, is to change your braking habits (so as not to build up those deposits).
Yet, if you don't bother to understand what causes the vibration, and you simply replace the rotors, you'll solve the problem quickly, but it will eventually return. And, most importantly, you'll be solving the problem without understanding the cause, which means you'll think your entire life that your rotors are warping. You might even vainly try to buy beefier rotors in the hope that they won't "warp" as much. Which means you'll be solving the problem with the right solution but for the wrong reasons.
Anyway, same thing with just jumping the red wire to the white wire. If I didn't understand first what the red wire was supposed to do, and what voltage it was supposed to have, and what effect it was supposed to have on the furnace, etc., then I would be remiss.
Of course, had I just disassembled everything and reassembled it, in this case, I would have solved the problem sooner, as now it's all working after I disconnected *every* wire, and reconnected them after cleaning them. I also tapped ever solenoid and relay I could find and blew the whole thing out with compressed air.
At the moment, it's working! Thanks to everyone! I very much appreciate the help.
http://farm6.staticflickr.com/5525/11318356035_47e7fcbdf4_o.gif
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On Wed, 11 Dec 2013 04:24:22 +0000, Danny D'Amico wrote:

OOps. Red to white!
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On Tuesday, December 10, 2013 5:36:20 PM UTC-5, Danny D'Amico wrote:

Turn furnace switch off. Connect the red wire to the white wire. Turn the furnace switch back on. If the furnace doesn't fire up, it's not the thermostat. It's unlikely it's the thermostat to begin with, so why waste time on all kinds of tests when there is a simple and very direct method?
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On 12/10/2013 6:08 PM, snipped-for-privacy@optonline.net wrote:

I think that Danny was an engineer in an earlier life. He's really a wonderful fellow, and I truly enjoy his posts to this list.
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On Tue, 10 Dec 2013 15:08:26 -0800, snipped-for-privacy@optonline.net wrote:

There is no furnace switch, that I know of. The wires come directly into the furnace from the outside. Of course, I can shut off a breaker ...

OK. I have the breakers off. I'll wait a few minutes now.
From another post, before I ruin something, is this correct? a. Connecting red to white should fire the furnace b. Connecting red to green should turn the blower on
Is this where I should make those jumper connections?
http://farm3.staticflickr.com/2849/11315437344_17e7793ca9_o.gif
BTW, normally I *measure* stuff (voltages usually) before jumping from one point to another; but I would need to know what *two* points to measure. Based on Stormin' Mormon's prior post, I'll read:
A. Red to White (AC voltage) ... is this what I should read? B. Red to Green (AC voltage) ... is this what I should read?
NOTE: I haven't finished reading everything, so, if I'm repeating, I apologize.

I've buttoned up the thermostat. It just took me a while to report back because I was trying to figure out how the darn furnace works and what the parts were...
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On Tuesday, December 10, 2013 7:26:39 PM UTC-5, Danny D'Amico wrote:

May be different in your part of the world and I'm not sure what that code actually says. But every furnace I've ever seen there has been at least one emergency switch with a red plate. Sometimes it's in the basement stairwell, with the furnace in the basement.

Yes, you can jumper from the red to the white on the right side, the R and WH terminals.

If you hadn't put it back together, you could have just connected the red and white together there.
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Some units will use a cord plugged into a receptacle. Usually this is only for control voltage, but in his case the control power supply also powers the blower. He might have a disconnect that he has not noticed. Usually this is required, but if in eyesight of the panel I don't think it is in this case.
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On Tue, 10 Dec 2013 20:54:12 -0600, Irreverent Maximus wrote:

As far as I can tell, there is no switch. Just a power cord plugged into the wall.
http://farm6.staticflickr.com/5477/11327971174_cd6604d692_o.gif
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On Tue, 10 Dec 2013 18:00:40 -0800, snipped-for-privacy@optonline.net wrote:

The California-specific PDF that I was sent says what you say, in that a switch must be within sight of the furnace; but it also allows for the door switch serving double duty as that shutoff.
Literally, that PDF says: "a disconnecting means must be located within sight of, and readily accessible to, the furnace. The blower door switch may be acceptable in some areas as a disconnecting means".
So, from that, I must assume the blower door switch is *my* disconnecting means. I'll snap a photo of the electrical wires tomorrow (in the daylight) to show you what mine looks like.
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On Tue, 10 Dec 2013 18:00:40 -0800, snipped-for-privacy@optonline.net wrote:

This is good to know because there are *two* red and white sets of wires! So, I'll jump the right set of red and white wires only.
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On Tue, 10 Dec 2013 18:00:40 -0800, snipped-for-privacy@optonline.net wrote:

I see now that the red (which is 24 volt power), is "connected" to the white (which is the indication of the call for heat).
In 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.
So, if I manually made those connections, it would bypass the thermostat.
(I didn't know this at all, earlier today ... so I'm just repeating what I learned today).
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On Tue, 10 Dec 2013 20:54:12 -0600, Irreverent Maximus wrote:

I'll look again tomorrow, by following the power wires, to see where they go - and if there is a shutoff switch that I didn't see yet.
It's dark and cold downstairs now, so I'll wait for daylight where I can snap better pictures for you.
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On 12/10/2013 7:54 PM, Danny D'Amico wrote:

The electrical code in the US demands that the furnace have a permanent connection to the power source...no plugs allowed. But when I asked the electrical inspector if I could put a plug on it so I could run it from a generator, he said, "no problem". The electrical code is very strict...except when it isn't.
He might have a disconnect

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Now, but when the unit was installed? I know of two units that are operated that way.
I am not saying that it is right, just that is how they were installed.
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On Tue, 10 Dec 2013 23:56:54 -0600, Irreverent Maximus wrote:

I must apologize for having never even looked before this morning to see how to turn off the furnace (I just hit the breakers up until now).
Following the power cord with a flashlight in the dark mouse-infested recesses, I see it terminates on an inaccessible back wall, in a normal 120V three-pronged power cord:
http://farm6.staticflickr.com/5477/11327971174_cd6604d692_o.gif
I pulled the plug this morning, and wished that I had not, since it's a bear to get back on the wall, because of the ductwork in the crawl space.
So, next time, unless it's an emergency, I'm gonna flip the breaker.
If I ever get a round to it, I'll see if I can hook up a switch on the outside of the furnace, where that wire enters at the door switch.
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On Tue, 10 Dec 2013 20:01:40 -0800, mike wrote:

Mine is in California. Built in the 1980s. It's plugged into the wall ...
http://farm6.staticflickr.com/5477/11327971174_cd6604d692_o.gif
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On Wed, 11 Dec 2013 03:54:03 +0000, Danny D'Amico wrote:

No shutoff switch. And the breaker is on another floor. So, most of the time, I leave it powered up.
I made the mistake of unplugging, this morning, and wished that I hadn't (since it's really not easy to put the plug back):
http://farm6.staticflickr.com/5477/11327971174_cd6604d692_o.gif
So, when I have the inclination, I'll see if I can put a normal 120V switch mounted on the side of the furnace.
I hate it when installers save a buck ... (their buck) ... as I agree; it should have a switch mounted on the side of the furnace.
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