Questions tagged [furnace]

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.

197 questions with no upvoted or accepted answers
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434 views

Furnace Connect G Wire

I have a dual energy electric/oil furnace that is wired to a thermostat with 2 wires R and W. I don't have any AC. Inside the furnace there is a switch relay to control the fan but it is not connected ...
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55 views

Why isn't my furnace igniting?

I noticed cold air from my Carrier 58SS furnace. The main burners were not lighting. The pilot flame was strong, but yellow. When I tapped on the gas valve, the pilot shut off. I removed the pilot ...
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1answer
99 views

York furnace not firing up correctly

I have a York TG9S080B12MP11A up-flow configured natural gas furnace. We have had the furnace since 2007. I am having an issue where the furnace is not starting correctly. When I power up the blower ...
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140 views

Thermostat not getting power (Nest E74)

I replaced an old Honeywell thermostat about a month ago with a Nest thermostat. Friday Nest started displaying an E74 error. I have two furnaces and two outdoor units, one for upstairs and for ...
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0answers
27 views

Rheem RGDG unit turns on w/thermostat off, blower come on and inducer motor switches off and on

I've having a problem with my rheem model rgdg-10nbrjr The air conditioning works, turning it on at night it blows cold air and the house indeed gets cold. However the furnace unit itself ...
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1answer
233 views

Position of dryer vent relative to gas meter and furnace intake

As part of renovations to our house (built in the early 70s) we are reconfiguring the laundry room and moving appliances to the opposite wall. The laundry appliances will now be to the left of the ...
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1answer
404 views

Unable to locate filter on Gas Furnace

Can not find where the filter for this furnace is. It is a gas Rheem Criterion II. Have watched YouTube videos but none look like mine. Thermostat keeps saying filter needs replacement.
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0answers
32 views

Garage Furnace Runs Only 45 seconds at a time

I have an older Janitrol Moffat furnace in my garage. It was converted sometime in the past from propane to natural gas. It takes quite awhile for it to heat up enough for the fan to kick in and once ...
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0answers
78 views

Replacing a motherboard on a Carrier 8000VS Furnace

Hi guys, I am trying to finalize the wiring of my new carrier motherboard. I have about four more wires to connect and the new motherboard is slightly different than the old one. The pictures I’ve ...
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1answer
11k views

Pilot won't stay lit after replacing thermocouple

The pilot won't stay lit on my furnace, when I release the button it just goes out. This started occurring after I did some gas plumbing and had to relight the pilot. I suspected the thermocouple ...
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574 views

Installing Ecobee3 with Trane Furance

I am installing an Ecobee3 and have found that, while the common wire exists, it is not connect to the furnace. The wiring schematic for my specific furnace can be found in this PDF There is no ...
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1answer
809 views

No power in r line after changed thermostat

I have a carrier furnace 2008, just changed my old thermostat to new nest thermostat, forgot to turn off the power. Now I have no power on my r line, checked short fuse still good, red light in front ...
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717 views

Constant cold air from vents with new downdraft furnace

Replaced with newer, high efficiency furnace and cold air constantly coming out of vents (except when furnace running). It's like the downdraft is totally free flowing and when windy outside very ...
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1answer
589 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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0answers
2k views

How can I reduce noise from an air handler unit in an open closet?

How can I reduce the noise from an air handler unit? I have a Goodman AR42-1 air handler unit in an open closet. The setup looks like this: When the air handler activates it sounds like this: ...
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2answers
2k 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
170 views

Why would my Maytag FG6RC high efficiency furnace restart in the middle of a heating cycle?

My furnace is probably 7-8 years old, and this heating season the furnace has developed a strange problem. The furnace starts normally, but before the temperature reaches the thermostat setting the ...
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1answer
6k views

how to change furnace filter (bottom return) for Lennox G43UF

I have a Lennox G43UF furnace and I am not sure if I need to have both a filter for a side return and bottom return. If I do (which sounds logical), where would the location of the bottom return ...
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1k views

Are w1 and w2 both energized during a second stage heat call from the thermostat?

Short version: does two-stage thermostat always close W1 circuit when it closes W2 circuit, or they might be closed independently? Long version: I have two-stage furnace, currently connected to older ...
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334 views

Why won't my condenser turn on when I run my heat pump?

I have a York Affinity condenser. When I run my heat pump, I expect it to turn on somewhere in the cycle but it doesn't. It generally does this once a year. The usual fix is to cycle the power of the ...
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2answers
21 views

HVAC / Furnace Evaporator unit in attic leaking cold air

We have an A/C (and heat) unit in the attic with force air ducts going to the ceilings in the rooms. I was in the attic today when the A/C turned on. I felt cold air come on my leg when I was near the ...
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1answer
53 views

Run Only The furnace fan

I have an old unit that has no control board. It works with a sequencer. (Coleman 3500A816) is it possible to wire it up to to be able to call only the blower to come on and not the heat as well? !
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17 views

Fan Only operation not working - gas forced air furnace

So i followed online guidance to enable "fan only" mode for my forced air gas furnace, Essentially that was to connect the "G" terminals on the t-stat and the furnace board. Seems simple enough, but ...
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1answer
23 views

furnace thermostat problem

Thermostat is reading crazy high temps when it is really 67. Furnace won't deliver heat. Fan works. Is it the thermostat (batteries replaced already) or the furnace?
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51 views

Part on furnace making scratching noise

This spinning part on my furnace (not sure what the part is called) is making this scratching noise. When one section of the part hits the area behind it, it makes that noise. Any idea how I can ...
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1answer
242 views

Sticky black liquid coming from Furnace / AC Unit

I have this sticky black liquid slowly leaking from my gas furnace / ac unit. I called an HVAC repairman and he wasn’t sure what it was. He said he thinks it’s an old drip pan made of tar (not sure ...
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23 views

Gas furnace ignites but then makes large knocking sound

My gas furnace will ignite, but after the pilot goes on for a moment it creates a large periodic knocking sound over and over again instead of the fan starting. I have my suspicions, but I wanted to ...
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70 views

Thermostats with or without variable temperature differential (swing)

I am looking at replacing my thermostat, and don't really need or want one with geosync. I am thinking of the honeywell RTH9585wf. Currently I have a lux that is not wifi but programmable. It ...
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34 views

Water Dripping From HVAC Furnace PVC

I have 2 PVC pipes coming out of my TRANE gas furnace. Today I noticed that one is dripping water from the top. Picture attached. Its a slow drip. What could this be?
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1answer
26 views

Furnace Inducer Whirrs on and off before igniting, works when I tap circuit board

My furnace gets the signal from the thermostat, then about half of the time, the inducer motor whirrs on and off over and over. Sometimes it runs continuously without ever lighting. When I open it up,...
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30 views

Lennox G51MP shutting down with Primary/secondary switch fault

I have Lennox G51MP-48c-090-06 ~14yrs old, starting up for first time this season. It is throwing error code: Primary or secondary limit switch open. Unit shows normal operation when powered up and ...
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3answers
428 views

Where to add a c-wire on my Goodman furnace?

I'm looking to upgrade my old thermostat and need to run a c-wire. Where would be the best place to tap into?
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353 views

Only getting 15-16 volts from Furnace R and C

I recently purchased a smart thermostat. Because it needed a common wire and I only had a 3 wire setup, I ran a new thermostat wire to my furnace. However, I now get only 15 volts (inconsistently, ...
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40 views

Furnace blower cutting in and out during A/C use

Backstory: I fired up my air condition for the first time this season (single family house) and felt lukewarm air coming out of my ducts. When i went outside i saw that the condenser was not turning ...
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1answer
104 views

Line to AC dripping at the furnace

My line from my exterior AC unit is dripping at the furnace. The dripping over time has caused rusting and we've had to replace the control board under it. It appears the root cause of the problem ...
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1answer
71 views

Furnace with no “C” connection

I have a mobile home furnace. This furnace only has a 4 wire connection terminal, G,W,R,Y. I also have a condensing unit outside with the 24 volt 2 wires coming to the furnace. I know I connect one to ...
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20 views

Furnace Pilot Flame ON constant but Main Burner never kicks in

I own an older furnace (Armstrong EG6F80DC12-6 -- natural gas, forced air, single stage, Honeywell S8600C Continuous Re-Try Module, VR8204A Gas Valve w/ Pilot Burner / Igniter-Sensor). It has been ...
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1answer
45 views

Furnace Pressure Switch Testing

I have a ComfortMaker combination furnace/AC for the back part of my house. The furnace kicks in, but never heats up. No errors are reported. Started troubleshooting and took a peek at the pressure ...
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1answer
52 views

Adding split AC to a Dayton oil fired forced hot air furnace

I'm trying to add split central air to my Dayton oil fired forced hot air furnace, mod # 3E268A. The manual clearly says it can accept this but the terminal block in the unit only has (4) lugs. TT and ...
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2answers
76 views

How to troubleshoot gas supply not making it to some appliances

I recently purchased a home and once utilities were turned on I've been having issues with certain gas appliances. Some appliances required a normal amount of time to get the gas flowing after being ...
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1answer
37 views

How can I control my furnace fan from a secondary thermostat?

I have a WaterFurnace geothermal system with upper and lower level zones. I recently added an outdoor wood burner and my issue is that I want to use a secondary stat to run the furnace fan during the ...
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1answer
78 views

Furnace Short Cycling

My furnace is short-cycling. I've tried the following: replaced the flame sensor Shorted the thermostat heat demand signal Checked the blower capacitor Checked the air intake filter Checked the ...
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0answers
79 views

Can I provide low-voltage power for an HVAC humidifier from a standard outlet?

I recently bought an Aprilaire humidifier to replace an old one that came with the house, which I thought was broken. After connecting the water (which does work and isn't clogged) and the wiring to ...
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0answers
558 views

How to stop the humming noise coming from my gas furnace when on Auto Heat?

My gas furnace makes a humming noise when on Auto Heat, like as if the blower motor or capacitor was bad. However, the blower turns on and sounds fine when thermostat is set to fan ON rather than ...
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0answers
83 views

Do I need to replace my pressure switch in my Goodman furnace?

We have a Goodman GKS9 Gas-Fired Warm Air Furnace. I've changed the air filter, cleaned the flame sensor, and checked the condensation pipes for clogs. They're clear. The behavior seems strange to me. ...
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1answer
63 views

burners out of sequence with blower motor

I have a Bryant furnace plus 90 model #398AAW036060D. I just changed the blower motor. In the last five years I've changed the main board, inducer board, pressure switch, and cleaned the igniter the ...
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288 views

Furnace not igniting with error E228

My furnace is Armstrong Air, A97USMV, today when turn on, the induce fan keep running but not ignition, then stopped with error code E228 (Unable to perform successful pressure switch calibration). ...
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43 views

How to Run Fan Only with Thermostar Furnace With G Wire

I have a Thermostar Furnace that works great for Heating our home. We do not have AC and do not want that. But, we do want to be able to just run the fan without heat. The W and RH wires were ...
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0answers
694 views

Where should I connect my C wire on Goodman GMP075-3 Rev.B

I am trying to install an ecobee4 to replace a digital battery powered thermostat. I removed the existing thermostat and found that there was a spare blue wire that was wrapped around the others that ...
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19 views

Do I need to replace the thermostat wiring leading to my boiler?

I have a boiler in an old building with four different apartments. There are two thermostats that call for heat from the boiler, and valves that direct the hot water to the respective part of the ...