The furnace is part of an HVAC or central heating system used to generate heat. Typically this is done with gas, a heat pump, or an electric element. For hot water and radiator based heating, use the boiler tag.

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Furnace Tries 2 or 3 times before staying on until reaching set temperature

I have noticed my furnace will cut the exhaust fan before lighting or sometimes start heating for a few minutes then stop. A few minutes later it tries again and will stay on until reaching the ...
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1answer
19 views

Furnace fan starts slow and is getting slower

here is a sound clip, start at about :55 or listen to whole thing! https://clyp.it/3h54oe2q model is tg9s060b12mp11 luxaire, which comes up as York most places. Anyhow, what's the best way to ...
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1answer
25 views

Central Furnace blower alwas on, even with thermostat disconected

A technician told me it was the electronic control board that has the blower relays on it , I replaced it and still has the problem, I've been reading here online about a limit switch for the blower ...
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6answers
36k views

Gas furnace kicks on then off frequently

A few times in the past week I will wake up to my furnace turning on, hearing a click when it tries to ignite, then turn off. This will happen for a couple minutes before the furnace quits trying. ...
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1answer
101 views

My goodman furnace is not igniting my burners

I have a goodman furnace and when it is calling for heat the ignitor comes on and goes off and comes on again and the burners never comes on what could be the problem
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1answer
10 views

RUUD Furnace blowing air but not heat

I have a RUUD furnace that stopped blowing hot air last night. I was thinking that it was the high limit switch gone bad BUT the coil ignites and lights but then goes out again after a minute, so ...
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1answer
185 views

Why would only 1/3 of my registers be blowing warm air?

I have a Coleman gas furnace in a wall space in my house which somehow shares the blower on my a/c unit on the roof because it turns on when furnace is called to start, though it does bump up after a ...
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2answers
601 views

Why is my new high efficiency furnace blowing cold air sometimes?

Why does my new furnace high efficient Payne furnace blow cold air,not constantly but at least 3 different times in a day, my thermastat is set on auto but when the weather is cold outside it will ...
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29 views

Where is this water coming from around my condensate pipe? (super confused)

Okay, so somewhat complicated story. When we bought our house 6 months ago the furnace was brand new but the AC unit was old. AC unit developed a leak that was expensive to repair, so we replaced it. ...
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601 views

Can I relocate my furnace exhaust?

When my new furnace was installed, the vent was put outside the house next to landscaping bushes. It has killed one of my bushes. It used to be vented up to my roof and out. Can I move this outside ...
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56 views

Where do I connect a C wire in a Rheem Furnace REAB 1415J?

I'm upgrading the thermostat with a Honeywell wifi one. I found all cables at the thermostat end, but can't figure out where to connect the C wire to the furnace (Rheem REAB 1415J).
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1answer
1k views

What could be causing vibration in my furnace?

I have a vibraton in furnace only when flame is lit. Blower motor seems fine. Is this vibration normal? Recently replaced inducer motor. Heat exchanger has been replaced once. Does not appear to be ...
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2answers
112 views

What could cause the blower in my furnace to come on?

Ok my blower just turned on, my propane furnace and it's not in operation due it being summer. My thermostat is set at 65 and the room temp is 78. The heater never actually fired it was only the ...
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5answers
95 views

How to Lower the Ouptut of Oversized Furnace

Questions I would like to lower the output capacity of my furnace if possible. How can I do this? Is it worth doing, or should I just live with it? Is there an easy way? Some ideas: replace burner ...
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2answers
41 views

Furnace keeps kicking off and on

My furnace runs for a few min then flickers and shuts off and then the system recycles and it fires back up and the process repeats over and over and over etc....
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6answers
6k views

How do I prevent ice stalagmites from building up on the furnace exhaust?

I have a high efficiency furnace that exhausts via a pvc pipe out the side of the house, the trouble is the moisture from the exhaust forms an ice stalagmite in my driveway in the cold weather. Are ...
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2answers
19 views

How much difference does hot vs cold air make with regards to an Aprilaire 600 furnace humidifier evaporation rate?

If I run the humidifier only when the heat is on, I get good evaporation. However, I want to consider also running it with just the fan running because our furnace doesn't run all that often. Will I ...
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43 views

Very old, Coleman, through the wall (double sided) mounted gas heater not working

My home was built in 1957, I had a new heat pump system put in (which I now hate) 7 years ago. It works fine in the summer, but in winter it doesn't heat the house very well. At the time, I kept the ...
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2answers
1k views

How is a high altitude natural gas burner different?

What is the difference between high altitude natural gas burner and conventional low altitude gas burner and why high altitude natural gas burner are needed?
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1answer
814 views

Connected C-Wire to new Smart Thermostat and Furnace board and still no power

I need help. I've been surfing the internet and have had no luck finding answers to my situation so am hoping for some guidance. I've seen other questions here answered but none that suit my ...
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1answer
102 views

Goodman gas burner not lighting

Goodman warm air gas furnace. Gas burner would not light.Status code light blinked continuously. Igniter glows red hot. I cleaned flame sensor with fine grade sand paper. Checked transformer line ...
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1answer
192 views

why does my gas furnace exhaust constantly

why does my high eff gas furnace exhaust run constantly ( when furnace isn't on ) the furnace turns on and off a few times before running then the blower comes on. now the exhaust wont stop without ...
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1answer
18 views

How do I wire my furnace humidifier so it comes on any time the fan is on?

I have an Aprilaire 600a humidifier from a few years ago and currently it's wired into my furnace with two control wires labeled "W/G" and "Cf". The "W/G" is connected to the W terminal on the ...
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5answers
205 views

Low voltage fuse blowing in furnace

I have an outside A/C compressor and indoor furnace fan combo in the attic. The unit was off and the 3 amp fuse was blown. I replaced the fuse and used the thermostat to turn the fan on followed by ...
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2answers
34 views

No water pressure in heating circuit

I have a natural gas hot water furnace and I can't get heat. First I turn up the temperature at the thermostat and I hear the furnace turn on, the supply line gets hot and half way down the line it ...
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1answer
628 views

my furnace fan stays on even when at temperature

I recently installed a 2nd generation NEST thermostat. I'm not home very often, but I was paying particularly close attention to the furnace after installing this thermostat and I noticed that the ...
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1answer
102 views

Why does my gas furnace run once then wont come back on until reset when temps are below 30 outside?

THE PROBLEM: My gas furnace will run one cycle and then not come back on until the switch is reset. Once the switch is reset it will kick on immediately run once and again I will have to reset before ...
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2answers
21 views

Furnace fan runs all the time

our furnace fan runs all the time It doesn't switch off when the furnace does and keeps blowing cool air I've replaced the filter and it's still running The thermostat (RTH6400D) isn't set up to ...
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3answers
6k views

What could cause a flame sensor to stop working so frequently?

Over a year ago after a month in our new house, we came back one evening to a cold home and after some googling, I found out that the flame sensor was dirty and the furnace was starting the flame and ...
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2answers
619 views

What could be causing my furnace burners to fire up, then shut off due to partially open door?

I have a 10 year old Carrier gas furnace that keeps shutting off every 24-48 hrs. First I thought it might be the flare sensor but then I checked the bottom door and it wasn't completely closed. I ...
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1answer
39 views

Goodman GM100 Failure to recycle

Our Goodman Furnace Model GM100 Serial# 9412063230 will start up and run but will not recycle after initially satisfying the thermostat. If you wiggle the gray,(ground), wire on the gas valve, it ...
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1answer
2k views

Where do I connect the C wire in my furnace?

I am upgrading my thermostat to a Nest, and would like to add a common wire. My current furnace controller doesn't have a C terminal, but the current thermostat wire has 2 unused wires (black and ...
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3answers
26k views

Adding a C wire to a new Honeywell WIfi Thermostat

I am trying to install a new Honeywell touchscreen WIFI thermostat and need to add a C wire to my terminal inside the furnace (using the help found at How can I add a "C" wire to my ...
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3answers
8k views

Does a whole house humidifier go on the intake or outlet of the furnace?

On what side of the furnace do I install the tank of the humidifier (the warm side or the return air side)?
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235 views

Lennox G40UH takes a long time for the heat to come on

The digital thermostat lights up with "HEAT ON" but it takes the furnace up to an hour to kick start. Once it does, it puts out heat. We set it to 69 here in Michigan with the outside temp at Zero. ...
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1answer
49 views

New Thermostat installed but compressor comes on immediately

I have a new Insteon Thermostat that I'm using to replace my prior Honeywell t-stat. This is installed to a relatively new HVAC system (both AC and Heat) that DOES have a "c" wire. I've attached the ...
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3answers
2k views

Wiggle, wiggle, wiggle wires on Furnace Pressure Switch makes it work — should I replace Switch?

My Furnace (a Rheem Criterion II Gas Furnace - model RGLH-07EAMGR) has had a problem for a while that we've just been living with but I can finally afford to do something about it. What happens is ...
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1answer
107 views

Correct Wiring for Furnace Blower Motor

After getting my furnace blower motor replaced, it now runs only in the following scenarios: 1. Mode "Cool" Fan "Auto" 2. Mode "Cool" Fan "On" 3. Mode "Heat" Fan "On" In other words it will not run ...
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2answers
60 views

Furnace fan works properly intermittently

My furnace fan sometimes stays on and runs continuously. I can stop it by flipping the breaker for the furnace on and off. It then stays off. When heat is called for, the fan comes on again and ...
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1answer
21 views

Can I replace the permanent filter in my furnace?

In my furnace (ruud ubhc-17j14sfa), there is a permanent, washable filter. It was there when we moved in 2 years ago. The house is about 10 years old now. The filter is pretty simple, more like a ...
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1answer
32 views

Pilot lights, but main burners don't on furnace with no flame sensor

I have a Rheem furnace in my house. It recently stopped working. It is the type where the pilot is not always on. Anyways, the ignition will kick in, and the pilot lights just fine. However, the ...
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5answers
15k views

Why would my Goodman gas furnace start but not stay on for more than 2-3 minutes?

I've got a problem with my 15 year old Goodman furnace. It starts w/o problem, inductor begins working, hot surface ignitor lights up and ignites the gas. Then the main blower starts working and the ...
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0answers
154 views

Why won't a NEST that shares control of a furnace with a conventional thermostat turn on the heat?

I have three floors in my home. The bottom floor has its own gas furnace and the 2nd and 3rd floors share another gas furnace. Everything was working great until I added a NEST to the first and ...
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2answers
36 views

Are my heat pumps using the right amount of power?

I'm trying to figure out if our two heat pumps are being power hogs and if there is something to do about it, or if they're operating normally. We bought our home recently and haven't been in it but a ...
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1answer
36 views

Can't get fan working on thermostat

I recently purchased a new thermostat. My old thermostat worked for heat (no AC either) but the fan wouldn't go on when I turned to "On" (in hopes to move some cool air from the basement up during the ...
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2answers
9k views

What could cause a Trane furnace to not start heating?

I have a newer (2007?) Trane XL90 (model: tdx2b080a9422aa)forced air gas furnace. The problem I am having is the burner and fan will not start. The thermostat is set at 67 degrees and shows it is ...
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1answer
3k views

Why would said gas furnace keep shutting off?

Seems that I have a gas furnace that is having some sort of heat/air sensing issue. Basically it shuts off after running for a minute or two. But if I remove the top plate of the furnace itself it ...
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1answer
43 views

HVAC Contractor Didn't Install Drip Pan

I recently got the A/C unit and furnace in my basement replaced. When the company came out to do the quote, they stated that they thought I should have a drip pan, and the proposal that they gave me ...
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2answers
31k views

How do I identify the C terminal on my HVAC?

How do I identify the C terminal on an HVAC, furnace, or boiler? If the terminals don't have a screw labeled C what should I look for on the wiring diagram? What steps should I take if a wiring ...
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2answers
16k views

Why won't my furnace turn off?

My furnace is running OK and heating the house. The problem is that I have the thermostat set to 66°F and it does not turn off when it reaches that temperature. I can turn it off manually at the ...