I have just been informed that our furnace is continually blowing cold air. The fan continues to run even when the thermostat it shut off. I had my wife flip of the “light switch” on the side of the furnace and that did shut off the fan. The thermostat is one of those cheap round mechanical style and the furnace is a high efficiency unit that is at least 20 years old. Of course I am in the process of flying back from Denver so I can’t view it 1st hand until this evening. I can do basic tests and repairs but obviously if this is serious it will require an expert. I’m just not sure whether to just have my wife call a technician now or hold off until I can mess with it a bit tonight. Any thoughts or suggestions (other than move)? Thanks in advance.

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Mr. Trump is unfit for our nation’s highest office.- JD Vance
If you committed violence on that day, obviously, you shouldn’t be pardoned.- JD Vance on the J-6 insurrectionists

Stay in a warm hotel tonight and let your wife handle it.

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If the heat comes on when you turn up the stat it may be that the thermostat is sending an improper signal to the furnace to run. You can test this with a multimeter. If you have voltage between the g and the c terminal 24 volts it's probably a thermostat thing.
If the heat won't come on but the fan stays on it's likely an open limit. Either a main limit or possibly an auxiliary limit in a blower compartment. If you put your meter on both sides of the limit and it reads 0 its closed and not likely the cause. If you read 24 volts across a limit its open and that's the problem.
If it's a high efficiency it should have an error code should there be a reason other than the thermostat that's causing the issue. Before killing power to the furnace see if its throwing a code. You can update this thread with a make and model and I'll try to help.

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"Play until it hurts, then play until it hurts to not play."
http://soundcloud.com/darkside124 HOF 2013, MM Champion 2014

Go tankless.

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Thanks, will do.

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Mr. Trump is unfit for our nation’s highest office.- JD Vance
If you committed violence on that day, obviously, you shouldn’t be pardoned.- JD Vance on the J-6 insurrectionists

Move

I think that's called an air conditioner.

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You do not talk to me like that! I work too hard to deal with this stuff! I work too hard! I'm an important member of the CSFMB! I drive a Dodge Stratus!

Yeah Zippy. Tell your wife to turn the AC off, and start making a pie.

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What is your approach to combustion safety?

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1-800-HEATING

HVAC / water heater... what’s the difference.

Should I change the anode rod in my water heater?

How about the johnson rod on your SAAB?

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So I had to reset the flame rollout switch. That seems to have at least temporarily solved the problem. The furnace has been running for about 1/2 an hour and the house is finally nearing “room temperature “. I also pulled the limit switch to make sure it wasn’t stuck and that solved the fan running problem. The question now is: is this a bigger concern even if it doesn’t happen again?

Thanks again btw.

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Mr. Trump is unfit for our nation’s highest office.- JD Vance
If you committed violence on that day, obviously, you shouldn’t be pardoned.- JD Vance on the J-6 insurrectionists

It'll happen again. The flame rollout switch means the flue is backing up or there is oxygen mixing post oriface which indicates a cracked heat exchanger. You'll either be cleaning out a bird nest or replacing the whole furnace. There's a small chance the switch itself is just failing but pretty unlikely.

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the world will always the world. your entire existence is defined by your response.

Rollout switches indicate either a lack of combustion air or a bad heat exchanger typically.
So... you can take the intake pipe off the furnace and see if that helps. It could be a clogged intake pipe.
If it's a bad or rusted out secondary heat exchanger you would confirm with a combustion analysis. High co and low o2 is likely what you'd find.
One way to test an intake pipe is to drop a golf ball into the intake from outside. The pipes should be pitched toward the furnace so if the ball makes it back to the furnace that confirms the pitch is correct and the pipe is clear. Exhaust should be the same way.
Also I've seen clogged condensate traps cause this. If water is backing up into the secondary it could be enough to cause a rollout to trip but typically the pressure switch won't close before that happens but I've seen it before so I wouldn't rule it out entirely.

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"Play until it hurts, then play until it hurts to not play."
http://soundcloud.com/darkside124 HOF 2013, MM Champion 2014

Also.... is this a carrier?

Aorrybit took so long to get back to you I'm out working.

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"Play until it hurts, then play until it hurts to not play."
http://soundcloud.com/darkside124 HOF 2013, MM Champion 2014

To check intake just run the furnace without the cover on the burner. Might have to tape down a door switch.

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the world will always the world. your entire existence is defined by your response.

This will likely cause other problems. Best practice is to cut the intake pipe a foot or so away from the furnace move the pipe ends apart and leave the combustion door in place. The pipe can be put back together easily enough with a fernco or glue in a coupling.

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"Play until it hurts, then play until it hurts to not play."
http://soundcloud.com/darkside124 HOF 2013, MM Champion 2014

at 11:30PM?

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It's an "Air Ease" Johnson (Armstrong) Ultra SX 90.

I had initially ignored the lower section since it only houses the circulation fan and that didn't seem to be a likely suspect. However, when I looked at the lower housing I found a piece of thin insulation up against the circulation fan. I assume it was supposed to be attached to the enclosure sheet metal for sound or thermal purposes, but certainly not against the fan. I am guessing this condition would be very similar to having a very clogged filter. I removed it and it seems to be operating fine.

There was also a fair amount of condensation in the exhaust drip leg which I drained.

Finally, it is an non-direct installation (no intake pipe to exterior).

Thanks to both you and Ike. It's been very informative. I'll update if the problem continues.

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Mr. Trump is unfit for our nation’s highest office.- JD Vance
If you committed violence on that day, obviously, you shouldn’t be pardoned.- JD Vance on the J-6 insurrectionists

The best way for your to keep warm is to go into your garage and start your car. Just leave it running until you fall asleep.

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what other problems? not arguing. i only know shitty residential furnaces through theory not a whole lot of experience

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the world will always the world. your entire existence is defined by your response.

Great analysis.

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An Ode to the Texas man who shot an Antifa terrorist:

Oh, he might have went on livin'
But he made one fatal slip
When he tried to match the Ranger
With the big iron on his hip

If you look at the intakes for high efficiency systems they typically have a baffle that regulates the flow of fresh air into the system or distributes it in such and such a way.
So theres these carrier systems, and they have the air intake that goes into a black plastic fitting under the burner enclosure. It's designed with a 2 inch opening on either side so you can pick which side to bring your air into based on the design of the ductwork. The unused side has a black plastic cap.
So a coworker of mine went out to a no heat call after a decent snowfall last year. The intake was clogged in such a way that it would have to be completely cut open but it was in a ceiling of a now finished basement so the ceiling would have to be cut out.
Now I carry barometric dampers to install in such situations but apparently this guy didnt have that so he just popped the other plastic cap off. Problem solved right?
I had to go back the next day. Ignition failures, namely carryover.
So I run this thing and combustion shows 220 PPM CO and something silly like 16% O2. I popped the cap back in, ran a nerf baseball into the intake with a fish line and pushed out the compacted snow on the intake (and ultimately installed the barometric damper) and retested combustion. 23 PPM CO and 9.9% O2. So having unrestricted intake air threw off the air fuel mixture enough to create incomplete combustion and also fuck up the carryover wing on one of the burners.
Install manuals typically state in an indirect vent to put 2 feet or so of pvc in on intake side. Must be a reason for it...

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"Play until it hurts, then play until it hurts to not play."
http://soundcloud.com/darkside124 HOF 2013, MM Champion 2014

Have water leaking out from furnace so I called someone. The furnace has a humidifier on it and it was completely caked with calcium and crud. Guy took it off and did his best to clean it. He didn’t have the right size filter to replace it. He checked a few more things and then left. I bought the filter and let it run. Still leaking. I called back, the gal puts me on hold and then comes back. She talked to the tech and he said it’s probably a corroded heat exchanger and you will likely need a new furnace. I couldn’t believe what I was hearing. Quite a turn of events. They are sending another tech this afternoon to diagnose. Even if I do need a new furnace I’m not buying it from these guys. Frustrating.

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Flew too close to the sun on wings of pastrami

"HVAC Question for Darkside" can be sung to the tune of "Love That Chicken from Popeye's".

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Power is always in the hands of the masses of men. What oppresses the masses is their own ignorance, their own short-sighted selfishness.
- Henry George

Not only does it fit but it was meant to be sung that way.

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Flew too close to the sun on wings of pastrami

and...now I want chicken.

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@audioidkid

Same thing happened to me a couple months ago. Corroded secondary heat exchanger. 16 years old but covered under 20-yr warranty but does NOT include labor. $1,200 to fix vs $6k for new.

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Did you have a home inspection or anything done before you bought the place? Not sure if there is anything you can do seeing as how you've been there just a few months, yeah?

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Had a home inspection so I can go back and look at that but we didn’t have any kind of insurance built in. It’s only 9 years old so maybe this other tech will sing a different tune. I just want to know where I stand with it so I can make a decision.

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Flew too close to the sun on wings of pastrami