thanks.

But is it draining CO or H20?

CO - Carbon Monoxide is a GAS,

IF your heat exchanger core plates cracked - the furnace will emit carbon monoxide in the vents / air ducts below.

IF CO [Carbon Monoxide] detected - shut the furnace it needs to be replaced. While it is possible to switch the heater core, cost of elements is more than this 80% furnace and the labor it takes to switch them is insane.

From what I understood you had damaged thermostat wire....

My thermostat wire is indeed damaged.

I suspect that I snapped the PVC when my ladder slipped; I simply hadn't taken notice that it was there.

OK, it's *way* narrowed down now.

Life happened and got in the way again, between physicians lining me up for tests and a threatened cold snap, and . . .

Anyway, it appears that I had *two* problems:

1) a bad thermostat, and

2) bad/kinked wiring going to the thermostat.

I fixed the broken pic, and thenI went to run new wire, but the old wouldn't pull into the attic. I'm not clear whether it's stapled or just the extra width of the second wire taped to the first is too thick to fit through the hole it shares with some romex.

But trying loosened a few inches at the thermostat, so I cut off a couple of inches, stripped, and . . . shorting R to G turns on the fan, while R to W turns on furnace.

Great.

Attach thermostat, and it won't turn on the fan.

But if I short R to G on the backside of the mounting plate, fan comes on.

Eventually I tested the thermostat after removing from wall. When heat should come on, I hear a relay click, and my meter across R and W shows a change from open to continuity. But when I put the meter across R & G and either set fan to on or wait a bit after heat comes on, it never shows a short.

Am I missing something, or did I manage to buy a thermostat with the exact same problem as my old one?

Connect R+G at the thermostat - - the fan [blower] should come ON.

Connect R+W at the thermostat -- heat should come ON, with the fan[blower], you do not need 24v on G during the call for heat. Most furnaces are smart enough to turn the blower on during a call for heat.

Yes, both come on when making those shorts.

But my thermostat doesn't produce a short between R&G under any circumstance--not after having one for a while on R&W, nor when setting fan to "on" instead of automatic.

And 10 minutes of running wasn't enough for the furnace to turn on the blower on its own,

thanks

hawk

(and, *really*? Autocorrecting "running" to "runic"?)

Get a Honeywell branded thermostat for testing.

I'm off to Lowes to pick one up right now.

But both the failed unit and the defective replacement are Honeywell . . . but I'm bringing a meter to test it before I drive home!

And that seems to do it, at least for the moment.

I brought my meter to test the new unit before driving home, but didn't have my glasses somehow (and still haven't found them; using a one-armed spare at the moment!). I got home and . . . it wouldn't even come on when I put the batteries in,

So I took *that* one back, and tested the next unit (the third) right there on the bench next to the return register!

And now it works.

Well, maybe. It didn't turn the fan off one time already, resulting in another trip to the breakers. So there may be (but hopefully not!) a followup on finding the relay U on the controller board . . .

(ultimately, I'll be building my own smart device with an Arduino, but there's a couple of projects ahead of it).

Thanks to all.

The end??????

aiieee! that was fast

the thermostat now turns it off and on. However, even pulling the thermostat doesn't stop the fan once it runs for a couple of minutes, and I have to kill the breaker (it doesn't come back on when the breaker is returned).

So it looks like I need to identify the relay on the controller. Any bright ideas?

It could be a bad furnace board, or it could be something wrong with the furnace like high limit switch (doubtful as it should not turn on ignition). Hopefully that board is not that expensive.

I don't have spurious ignition,, just failure to turn off fan (even with thermostat pulled

There is that flashing LED in the middle of the board, does it have a heartbeat or it flashes some number fast flashes and so many longs....

do I want to look at this after power, after it turns on, or after the fan fails to shut off?

thanks

After the fan[blower] fails to shut off.

OK, I'll bring it about tomorrow.

edit: hmm, do I need to bypass the case shutoff button before this happens. Or, will the shutoff from opening he door lose the code?

Normally there is a plastic cover that allow you to observe led without opening the blower compartment. But if you do want to open it for some reason - use electrical tape on that switch.

I don't seem to have such a cover (but it wouldn't surprise me at *all* if the clowns that put this in managed to mount it somewhere it can't be seen.

This morning, we turned it on to warm the house, figuring I'd go up and watch for codes and then kill the fan with the breaker--and it shut off properly.

??

So we'll see what it does throughout the day.

Could the relay have gone sticky from non-use, and is unsticking as it's used? That doesn't sound likely to me, but . . .

And I assume those black boxes at the lower left on the board picture of twelve days ago are the relays?

It's also occurred to me that I can by a 24vac 10A relay for under $10 and conceivably run it directly from G to run the fan . . .

Edit: for crying out loud, now the fan came on by itself, and again wouldn't turn off without hitting the breaker, even after pulling the thermostat . . .

OK, it's blinking eleven times short.

And it seems that I *do* have a plastic port under all that dust!

I'm guessing that the model number of the board is under that wire, a couple of lines below "Emerson" . . .

is moving or removing the blower delay jumper likely to do anything?

And I'm guessing that the white button will cause the LED to give the last message if I open the door and the message stops?

I found a guide at https://climate.emerson.com/documents/21v51u-843-installation-instructions-en-us-1645268.pdf that seems to suggest that this is "Limit switch open – possible blower failure overheating limit", and "Possible blower failure, restricted air flow through appliance or duct work. Verify continuity through limit switch circuit and correct overheating cause."

My blower is pushing normal amounts of air.

thanks

hawk

>"Limit switch open – possible blower failure overheating limit

That is what I though initially...

It could be high limit switch or it could be the flow. Make sure that ALL supply registers are open, no coats stuffed in the furnace return, remove your filter, would replace high limit switch, like $10..

We have a single 20" downward facing intake in the roof of the hall that has a 10 or 15 foot run. I'll toss a little plastic ball from the blower chamber in the morning.

Aside from blowing dust, would there be any harm in running without the filter to test the system?

Is the high limit switch the thing in the green circle?

So just unscrew, unplug, and take to HVAC place?

thanks

>So just unscrew, unplug,

Yes,

>HVAC place

Most places will require you have EPA cert on file and will NOT sell. Plus I know many ppl get intimidated. May I suggest amazon or web sellers.

>I'll toss a little plastic ball from the blower chamber in the morning.

For what purpose?

>Aside from blowing dust, would there be any harm in running without the filter to test the system?

For testing NO. You can run it without a filter, just don't run it for weeks.

>For what purpose?

checking for obstruction.

When the gang of clowns installed it, the conduit (?) from the plenum to the front of the house was turned to the side and muffled by the insulation rather than connected to the next segment. It wouldn't particularly surprise me if they did something stupid with this line.

Thanks; I'll pull it in the morning and get another,.

Looks like ol White-Rodgers 80%, non-condensing, the honeywell valve has only two wires I doubt it is two stage, three burners pretty small. That thing was barely worth $400 when it was new. Oddly it has CSST NG line instead of the back pipe appears to have leaked multiple times.

definitely not two stage. We're AC dominated around here--it will dip below freezing a couple of times, and every few years might go all of the way down to 20 overnight. But 115 is just another summer day, and not the hottest of the year . . .

>Oddly it has CSST NG line instead of the back pipe appears to have leaked multiple times.

I'm not sure what this means.

The contractor was flaky, didn't always show up, and stopped returning my calls. License was pulled or surrendered not much later.

We have, well, an accordion valve of conduit out the top of the plenum because he punched the wrong hole; he ran separate lines from the plenum to each bedroom and just one to the front of the house; the collapsed conduit to the front of the house; pulled my expensive 7 day thermostat and replaced with a basic unit without asking--and lost the base; ran the CO line at the wrong angle , , , so nothing really surprises me at this point.

As the last kids finish college and presumably move out in a couple of years, I assume we'll be replacing the air with multi-split eventually, or maybe just a mini split for our bedroom and keep the rest. We don't use the AC much, as we have the monster swamp cooler, so replacement may not be for a long time off.

But my wife *really* likes to be able to warm the house back up in the morning, for some reason. :)

I'm starting to feel like the sitcom writers are messing with me . . .

I went into Grainger only to discover that the switch had fallen out in the dentists chair. Any year but 2020, "A piece of my furnace fell out of my pocket while the dentist was working on me" would qualify as one of the strangest things all year . . .

Anyway, I got the piece pack, handed it to the gal at Grainger, and she located the current version rather quickly. about seven bucks later, I came home and installed it.

I even thought to check the LED, which was happily green.

testing with jumper, R to W lights the furnace, and R to G . . . simply makes this controller (?) on the side of the fan buzz and vibrate:

I'm not sure what it is (filter? starter? with three wires, it's not just a capacitor or condenser), but I figure it controls the fan, and either gives it power or not.

The buzz is enough that I can hear it downstairs at the thermostat, probably about 15 feet away from it.

Is it something I can just hand over again and get a replacement?

thanks

hawk

https://www.newcentralairconditioner.com/

Engine running hot.

One of the first symptoms commonly associated with a bad or failing cooling fan relay is an engine that runs hot or overheats. If you notice that your engine is running at higher temperatures than normal, that may be a sign that the relay is not functioning properly. If the relay shorts or fails, it will not be able to supply the power for the fans to operate and keep the engine running at normal temperatures. Abnormally high temperatures can also be caused by a variety of other problems so it is recommended to have the vehicle properly diagnosed to be sure of the problem.

2. Cooling fans do not function

Non-functional cooling fans are another common symptom of a potential problem with the cooling fan relay. If the relay fails, it will be unable to supply power to the fans, and as a result they will not operate. This can lead to overheating, especially when the vehicle is at a stop, where there is no forward motion by the vehicle to pass air over the radiator.

3. Cooling fans stay on at all times

If the cooling fans are staying on at all times, this is another (less common) symptom of a possible problem with the cooling fan relay. If the relay shorts internally, it may cause power to be permanently switched on, which will cause the fans to run at all times. Depending on the wiring setup of the vehicle, this may cause them to stay on even when the vehicle is off, which will drain the battery.

uhmmm . . . this is a household furnace, not a car . . . (but I have successfully replaced the fan clutch that someone added to my '72 Eldorado convertible . . .)

Deserthawk, I've been reading this thread giggling the entire way and commenting to my wife it's like reading an abbott and Costello script with a touch of Jerry Lewis in every post. LOL.

I'm not getting involved, you and BT have it well under control and can't wait for tomorrow's episode.

as much of a ham as I may be, and so happy to entertain, I surely hope that tomorrow is the series finale!

:)

I guess you do not get a break on that thing. Here I could have found you a replacement: brand new for probably like $350.

On that capacitor, look for the evidence of bulging or leaking on the side with a contacts. Be careful, turn the furnace off and discharge that cap - otherwise it packs some jolt.

For a noise: I would inspect the motor itself - it probably has bearing or windings ready to fail. When a furnace is off [either discharge the capacitor or wear rubber gloves] spin that blower good and listen for a scratching noise, check that pcs motor for play... In the past they had oiled bearing but all moderns used sealed so they can not be lubricated.

Anyway your furnace should be working now.

CSST - is that yellow flex NG pipe entering your furnace and connecting to that Honeywell valve. I always thought it has to be hard pipe (black iron with a leg trap). Our local building inspector will 100% tag that install. Here we are not allowed to use plastic CSST next to furnace burners..

>I guess you do not get a break on that thing. Here I could have found you a replacement: brand new for probably like $350.

do you mean the fan, or the furnace assembly?

The furnace definitely fires up now, but the air doesn't go anywhere . . .

no external sign of leaking on the capacitor(?).

When the fan tries to come on, only the external device vibrates; the housing of the fan doesn't seem to have any at all.

I'll check the yellow pipe; I had thought that it was metal, but inspecting it wasn't even on my radar.

Around here, a permit is not needed to replace like with like. I don't *think* there was a permit at all for this installation--but now I'm not so sure (in fact, doubt) that going from closet to attic was "like" for that, and I sure don't remember an inspection.

I'll go up and inspect in the morning. Will a large screwdriver across the lugs do for discharging the capacitor? (I had assumed that those were power going into the fan, with the green that disappears behind it being the signal).

entire furnace. https://www.youtube.com/watch?v=MozDlcC_1m0

The fan seems to spin freely as I reach in the top.

Using a cheap multimeter with a 9v battery, after shorting the capacitor, it took 4.5s for the capacitor to go from a reading of open to 200kohm, at which point it had a charge of about a quarter volt.

While in circuit, it vibrates loudly.

the cap:

And video of it buzzing, with some of spinning the fan starting at about 20 seconds.

http://dochawk.org/furnace/IMG_0023.MOV

[hmm, should get around to updating that to https . . .]

The buzz is loud enough that I felt it with my lap playing back on my laptop . . . I didn't notice them while up there, but on the video, it sounds like some clicking on the fan, even though it feels like spinning free

That's it! just a buzz, no explosion or firetruck sirens witch is a good sign. What little trick is coming next Macgyver? I'm done fun'in around, I know that sound well but I'll let BT fill you in.

Hmm your AC motor is buzzing but not spinning?

replace the cap (running cap), replace the motor. Only two components.

https://www.amazon.com/370-440V-Capacitor-Electric-Compressor-Furnace/dp/B079SMV9K2

Grainger will have it as well: both cap and motor

the motor isn't buzzing, it's the cap. The vibrations are significant.

The bright side of having these medical appointments up north is it's easy to stop at Grainger on the way back :) . . . so I'll start with the cap, as I assume it's cheaper, and it will take some balancing and maneuvering to get the motor out .

I believe you stated the current problem is the new thermostat can start the blower motor but cannot turn it off. If that is the case then i don't see how a bad capacitor would cause this problem.

no, it can't start it at all any more.

for a while when it *was* starting I'd hear the buzz for some seconds before the fan spun up, and just figured that that was the fan itself.

it fails at 7 (although I'm not sure what the draft motor is, but the furnace lights ).

At 7, the cap just starts buzzing, and even if given a few minutes, the fan never starts.

I get the same buzz with no blower when I simply short R to G (or flip "fan on" on the thermostat).

(at the earlier stages, the fan was coming on, albeit with the initial buzzing, and sometimes wouldn't turn off.)

I win!

I picked up the capacitor at Grainger ($5 - something), put it in, plugged it in with R&B shorted at the base, and the fan came right on.

I put in the thermostat, and it has turned on and back off at least three times.

Thank you, thank you, thank you!

Congrats

I kind of think you have contributed more than I, but thank you. your help was amazing, and I know far more about these contraptions than I ever expected.

Gee, it was nice waking up to a warm house this morning . . . at the appointed time, it fall fired up while we were still in bed . . . for the first time since last winter.

I chose the particular answer to future as it's a wonderful checklist. It probably even deserves a sticky post of its own (although probably not as critical when there's a single problem that stays put and can be described . . .)

Good work for keeping at this until resolved. At the end did you have a bad capacitor and bad wiring? Did you determine if your original thermostat also had a problem?

At the end, *all* of these were confirmed:

1) bad wiring to thermostat. It was quite kinked, and intermittent. I cut off an inch or two and re-stripped.

2) original thermostat fan relay was bad. I confirmed this with a meter.

3) first replacement thermostat had bad fan relay, again confirmed with meter.

4) second replacement thermostat was just plain DOA. (I tested the third in the store before leaving!)

5) bad capacitor.

I don't have confirmation that the high limit switch was bad; behavior didn't change after I swapped it out.

The controller board seems off the hook for the moment, although I'm still unclear how anything other than its logic or fan relay could have kept the fan going after pulling the thermostat from the wall. I am kind of curious about this.

1) and 2) had clearly manifested from time to time in the past, but got shrugged off when they only happened once.

5) seems to have been showing itself for a while. The slow start was consistent with the monster 1hp motor on my swamp cooler, so it, along with the buzz (which I took to be slowly spinning up) never stood out. I'm pretty sure the cap got louder after the last couple of weeks, but . . .

[the next HVAC related project in a few months is probably a scoop for the swamp cooler. A standard grate seriously cuts the flow. Being open and venting down in our entryway results in most of the flow going to the front of the house and a couple of bedrooms getting so little flow that air comes *in* the windows (aside from being ugly and looking tacky). I'm thinking in terms of a two foot panel that comes down a few inches or foot on one side and a foot or foot and a half or so towards the hall, to rent a lot in that direction. (This year, I used a spare 4x8 panel to block flow into the living room. I'll eventually build a sliding barn door type panel, but that's enough issue). But for now, we'll enjoy the warm house, and not paying for the electricity for three space heaters, freeing two for the hothouse (and just in time!)]

If your fan is in auto mode and the furnace blower continue to run after burners stopped ... it could be a symptom of a high limit switch failure.

If so, it's fixed :)

I want to say that it also happened when I simply ran it with the thermostat override, but I'm really not sure at this point . . . edit: come to think of it, the chamber likely would have still been warm from the fan just having done the same thing after running the furnace, so it's not an independent failure anyway.

Odd how with so much failing or poised to fail that it generally worked for the times we needed AC this summer (but, again, that wasn't a lot). I do, though, think that there was a round where the fan stayed on when the AC stopped.

Or maybe moving the wire to dismount the thermostat was the last straw for the crunched wiring.

followup a year later . . .

For those doing such a repair, note that . . .

A couple of weeks later, my kdis called while I was out of state. Again, no heat.

The access doors ha not ben *completely* closed, it seems, and worked their way out in this time, releasing the dead man's switch. So save a trip back up, and make tripe sure they're properly seated and latched.