Why is my fan running all the time with no heat

[@dancallahan2590]

Hey folks,this guy is good.Mr.Grey I had similar problem,the furnace was short cycling,shutting off the gas and starting again.But it was not the limit switches,it was the air filter that was too thick and restricting air flow. Thanks for helping us folks who can fix simple problems. You are the best.

[@beephoon7489]

You make the best video on oil furnace. I never get tired of watching your video. Very well explained and detailed information

[@grayfurnaceman]

You must have a boring life. lol GFM

[@Molly-cl5pd]

Oh thank you so much sir!! You simplify the instructions so well I was about to tear my hair out!! I am so grateful!!!

[@grayfurnaceman]

Glad you got it going. GFM

[@biartspencer]

Thank you so much for your help with my furnace. Limit switch must've activated due to a clogged air filter. Probably saved me $150.00 and the embarrassment facing the HVAC guy. Glad I wasn't too busy to deal with it myself.

[@Yophillips3272]

This is the 2nd furance you helped me fix. Simple and straight to the point.

[@waynemiles7027]

Tank you Mr. Grey for all you do for the hvac community.

[@grayfurnaceman]

Welcome GFM

[@tonylaracuente7112]

thank you mr. gray furnace I learned a lot from all your videos in the past few years thank you very much

[@grayfurnaceman]

Welcome GFM

[@ronbrooks7808]

Thanks for the video, my relay was bad, board even had a little burn on it. $70, back in business. Cheaper then my $165 home warranty deductible!

[@grayfurnaceman]

Not a fan of home warranties. GFM

[@jerryluth1533]

Your an excellent instructor, thank you for taking your time to help, Jer

[@grayfurnaceman]

Thanks for the support. GFM

[@tonypointer7026]

Great video

[@Mud55]

Thank you Sir! That was well explained and the switch was the exact problem.

[@augustinejames1168]

I like that this is a simple fix

[@tre2472]

Thanks!! This is my problem with my furnace.

[@edbtzkhud]

Trey K replace the control board

[@dcmoor4662]

How about a bad relay on your control board. I encounter this on a york diamond 80 the fan was on all the time in heat, cooling, and when t-stat was in the off position.

[@intelin123]

I learn so much from you than from my job

[@Jeff_S...]

I've had quite a few with packed evaporator coils limiting airflow and coils with whole sheets of paper on them, that somehow made it all the way through. I've heard of dirty heat exchangers, but never found one myself.

[@slappahoe8493]

Yes sir! I’ve had the same problems and finding the A coil packed

[@geojor]

always great, thank you ...

[@RC-Heli835]

I just had an easy one finally at my rental house. A mouse had chewed a hole in the vacuum line on the vent motor and the igniter wouldn't glow to start the burner. A while back the AC compressor had to be replaced at 1600 bucks. The year before that it needed a capacitor and Freon so nothing I could do.

[@JoelGonzalez-us5hj]

Thank you mister...you help me a lot

[@grayfurnaceman]

Welcome GFM

[@psicopatalucifer]

Nice information.

[@acrepairnearme]

Thank you. Evaporator coils also can be clogged.

[@speway]

First and for most a big thanks you to you Mr. Grey and a Happy New Year! I find this new year, at about 3 am, that a hum is coming from my vents and no hot air....no cold air either. Thermostat is reading 51 degrees F at present and outside temp is 14 F here in DC. It's about to get cold in here. I have family here from Philippians experiencing their first winter EVER. My issue is not rectified but I think the answer is found here in this vid.

[@grayfurnaceman]

Look for error codes on the furnace. Should be a small window in the fan cover to see the codes with a key on the inside of the door. GFM

[@speway]

You, my friend, are a whole lot of awesome! Forgive the latent response. I went into survival mode and purchased 7 medium room portable heaters to take the edge off.....1952 home no insulation just wall cavities. It was still cold. Regarding the error codes, my system does not have a read-out as such. The bread board does not have a digital read-out nor does it have any LED that would denote error. Nonetheless thanks to your vid on "Limiter Switches" I am back up and running real nice and toasty like.....hence my first statement. You literally make the world a warmer place...and or cooler place respectively.

[@grayfurnaceman]

Thanks for the support. GFM

[@StorminNorman-sm8ro]

My house is new and when it reaches the limit on the Thermostat it just starts blowing air and won't stop until I switch it off or turn the set temp down.

[@jgharts4949]

Thank you!

[@tonyb9785]

For me the ignitor and flame sensor needed cleaned with high grit sandpaper, I found this after looking at the code my furnace board was throwing (blinking light, google it), which pointed to the issue; if you're having problems, check the code if possible.

[@dirktyssen5211]

Our inducer motor never shuts off even when there is a call for ac. Heat turns on once , but that’s all she wrote until I kill the power to the furnace and then turn it back on. I am assuming this is because having the inducer motor running all time does not cause a neg pressure reading for the pressure valve to close and start the heating cycle. Everything checks out good with a meter for resistance including the limit switch. Is it just the relay on the board for the inducer motor stuck on? Any help would be much appreciated Dirk

[@grayfurnaceman]

I would first look at the relay. GFM

[@RoadVentureRV]

Thanks man this was supper helpful 😎❤👍

[@grayfurnaceman]

Welcome GFM

[@markparkus6988]

yes tyvm was the air filter

[@rgo5062]

Can this happen if the blower motor is going out?

[@grayfurnaceman]

It could happen, but very unusual. GFM

[@castingflaw]

Mr.Grey.I have a Rheem criterion II gas furnace, guessing it was installed before 2007.Its now 9/2018,we have been running the A.C. with the warm weather and the blower motor (the small one that starts up before the glow plug lights up in the winter) will start and then stop, we have a old dial type thermostat.If we need to replace the thermostat will there be a problem if we have to go to a new style?

[@douglasbrown1261]

I have a crane rooftop furnace on a commercial roof what caused the inducer motor too working

[@grayfurnaceman]

I assume that's Trane. Is the inducer running all the time? GFM

[@missiletm]

Our blower runs automatically in our vacation home (mobile home) in Palm Springs during the summer when we’re not there and the inside temp is over 85 degrees or so unless we shut off the breaker when we leave. We’ve recently installed a smart thermostat to turn on the AC before we arrive but it’s useless if the breaker is turned off. Is there a way to fix this so the blower isn’t constantly running without killing the breaker?

[@dragonfly1414]

Hello Mr. Gray my heater setting 75 but keep running to 90 and way to heat inside the house, any advise will be appreciated, thank you

[@grayfurnaceman]

Electric, gas or oil? GFM

[@deborahshingleton2628]

that bottom part moved on its own did you see that?

[@dcobhc]

Thank you for another great informative video!

[@grayfurnaceman]

Welcome GFM

[@craignehring]

Say there GFM, what is a recommended cleaner for fan wheels? I imagine it depends on the type of filth collected?

[@grayfurnaceman]

I use an industrial cleaner made for coils and fans. However, a household grease cutter type cleaner will work well. GFM

[@TheChug]

Is there a limit switch in Electric + Heat Pump furnace? My furnace works on heat pump, but when it's too cold for the heat pump, it shoots cold air on Aux Heat... thanks!

[@grayfurnaceman]

There are limits on electric furnaces/air handlers. I would be looking for kicked off breakers or control problems. GFM

[@TheChug]

@@grayfurnaceman oh OK, breakers are OK. The damn air handler is in the attic... This morning it was blowing colder air than indoor temperature and when I switched it to EM Heat, it blowed air at roughly 68 degrees... I shut it all off and using the room rads now... I'll look to install a new unit inside the house. I think it was stupid to have it installed in the attic by the previous owner... Up here in Canada, it get real cold. Thanks for your quick answer.

[@mazenblue3790]

Thanks for the video. I have an old Crane furnace and the fan belt blower motor never shuts off. It will stay on as the furnace heats up and not turn off at the end of the cycle. It's not the thermostat because I changed it out and the blower remained on. It has a honeywell limit switch like the one in this video and it is set to auto. Do you think the limit is bad? The temp relay clicks on and off when the fan is turned on, even though it's already running so I think the relay is good. Any advice would really help me out! Thanks

[@grayfurnaceman]

This sounds like the fan and limit has failed. Try hitting the ductwork near the fan and limit. If it shuts off, you are certain that is your problem. GFM

[@mazenblue3790]

@@grayfurnaceman Thanks a lot, I'll give it a shot. Will hitting the ductwork reset the switch or something?

[@grayfurnaceman]

It breaks the contacts loose. GFM

[@mazenblue3790]

@@grayfurnaceman thank you. It was a bad fan limit switch.

[@1cleandude]

Thank you Mr. Gray I appreciate your videos and they are very helpful!! My Trane unit purges, ignites and then the blower comes on. After getting to the set temp the gas shuts off and the blower continues to run until manually disconnected. It would normally run for approx. 2 minutes as a post purge/cool down. Would a limiter cause the blower to continue running? The error light is 5 blinks however your Error code video did not elaborate on this particular code. Any suggestions? Thanks again!

[@grayfurnaceman]

Its possible the unit has locked out on flame failure or a pressure switch problem. The 5 blink means the flame rod is sensing flame when there is no power to the gas valve. Are you sure its 5 blinks? If the flame goes off, it should not be sensing flame. GFM

[@1cleandude]

Thanks for the reply; yes I just looked at the IFC and it blinks 5 times pauses and blinks 5 times etc. When the furnace is running I have 25 volts at the limiter. When the flame shuts off I have no voltage and the blower keeps running with the 5 blinks at the IFC! Could it be a stuck relay in the IFC; the unit is 10 years old. Thanks again! David

[@tylersalisbury872]

My electric heat air handler had it's sensors go off due to high heat but the filter was new and had enough air flow to it but the sensor kept randomly going off and had my neighbor come over and test the airflow and was correct.. we since replaced the heat strips because the relays stuck on and caught fire..

[@grayfurnaceman]

The shutdown was probably due to one of the sequencers (relays) sticking on and overheating the furnace which will result in limit switches opening. GFM

[@brianlange9356]

Hello GFM, Your videos and website have saved me service calls and money in the past and allowed me to become pretty comfortable at troubleshooting and working on my Goodman GMH80453ANCB. I truly thank you for that. I have a problem now that has me puzzled and sounds possibly like a limit switch issue that you describe here. I will attempt to provide some detail here. The heater comes on with the thermostat, the inducer cycles up, the pressure switch actuates, the ignitor glows, gas flows and the burner lites. (2 burners) The burners remain lit for about 15 seconds and the gas shuts off but the ignitor almost immediately begins to glow and the cycle repeats until the thermostat is satisfied. The problem is that the blower is almost constantly running through this cycle. This is causing the air being pushed to be luke warm if not just room temperature. Filter replaced and the symptom is the same with 2 control boards.(on hand for a previous problem) I have just replaced the limit switches for the heat ex-changer 220 degrees and the blower 120 degrees. I do not see any indication of a problem with the heat ex-changer such as off color or erratic flame, blow back from the fan etc. As I said, I am puzzled and about to call a pro as this is causing the heater to run almost constantly and not able to heat the house. Sorry to be so long winded.:)

[@grayfurnaceman]

I would try temporarily jumper the limit (and I do mean temporarily, do not under any circumstances leave the jumper on), If the problem stops, you may have a failed heat exchanger. The heat from the burner is contacting the limit directly. GFM

[@brianlange9356]

Thank you for the response. I jumped the 2 female spade connectors to the primary limit switch. The initial burn cycle lasted about a minute. I was able to run upstairs to check the air and it was obviously warmer. However it then returned to the previous cycle of the burn lasting only about 15 seconds. I do not remember exactly what a normal cycle was like, but I assume that even this last cycle while jumped would not be normal.

[@grayfurnaceman]

I assume that with the jumper installed, you reverted back to the 15 seconds on condition. Have you jumped out the thermostat? GFM

[@brianlange9356]

No I have not. Just jumper the 2 wires?

[@brianlange9356]

I jumped the thermostat, while not exactly the same, it is still not normal. Burners lit following normal startup cycle. Burners ran about 30 secs, immediate ignitor glow, 6 sec burn, ignitor, 13 sec, ignitor, 12 sec, ignitor, 12 sec, ignitor, 9 sec, ignitor, 14 sec, ignitor and so on.

[@leslielambert4500]

I have A criterion gas furnace blower will not shut off even from thermostat I have to replace the panel to shut it off no heat, but I did notice the batteries were dead in thermostat I change them

[@leslielambert4500]

Anyone help or had this problem

[@albotiger7268]

If that’s the symptoms then it sounds like you have exactly this problem same problem with the High Limit switch. If the fan has run for a long time and it doesn’t reset then your switch inside is probably a manual reset and should have a button you can push in which would close the switch and bring the heat back on

[@defiantlion231]

Could loose screws on the fan grill cause problems? I found a few screws loose laying just b-low the back burners & 1 n the front. Could a wire possibly be connected to say a screw?

[@grayfurnaceman]

It certainly could. Depends on where they came from. If you send me pics of the screws I may be able to tell you if you should be worried. Send to [e-mail] GFM

[@yamilrodriguez5918]

I am trying to run the blower ON with the furnace OFF(Luxaire TM9V) to move the air around the house but it will not work. It only work on the auto possition with the furnace working. Any ideas how i can fix it.

[@grayfurnaceman]

Have you shut off the power to the furnace? The fan will not work with the power off. If your furnace is on and the fan, when set to "on" will not operate, the "G" terminal at the furnace is not connected to the "G" terminal of the thermostat. GFM

[@yamilrodriguez5918]

Thank you for your reply. I will check the G terminal connection tomorrow. Power is OK. The furnace is working and fan works with it. Just trying to operate the fan manually to circulate the air on the house.

[@yamilrodriguez5918]

@@grayfurnaceman Hi GFM checked the G terminal at the furnace and it is a green wire and at the thermostat is the same. At thermostat(White Rodgers model#1F78) W- white, RH-black, RC-red, G- green, Y-orange .

[@grayfurnaceman]

@@yamilrodriguez5918 Jumper from "G" to "R" at the furnace. If the fan works jumper "G" to "R" at the thermostat. If it works, it is the thermostat. GFM

[@yamilrodriguez5918]

@@grayfurnaceman Hi GFM tried the jumper. No luck. after checking the schematics of the furnace looks like the power to the fan is controlled buy the ignition sensor. No ignition no power. i guess it is the design in this 2 stage furnace. I will look if i can bypass it running power directly to th fan wit a switch on the outside. But that will be on the summer time. Thank you for the help.

[@justincuevas8529]

My issues is with a furnace that’s blower stays on during auto without calling for heat. It gives an error code for the flame rollout but instead of just buying the rollout what can I do to either bypass the rollouts or make sure that is the problem?

[@vn8410]

I measured continuity for this device 5'' old style and figured out that is bad. Ordered from amazon new one 5" with fan button and connected, my thermostat was off/heat was off, when I turned power on blower motor started working and heat come up, gas valve energized and something started melting. What was wrong why it used to do like that? All wires were connected properly.(((

[@grayfurnaceman]

Beats me. Sounds like you wired it wrong. GFM

[@sotog1217]

have a carrier 58SX100-cc sometimes just here inducer motor running so i look in the little window by burners no pilot if i disconnect hose from presure switch and blow through hose into furnace it will light and work any idea

[@1lefty123]

Anyone in the business uses low to medium restricting filters and change them faithfully. High restrictive filters strain the blower and put you at risk for high limit trips.

[@themancmt]

Couldnt you just bypass the switch all together by hooking up the 2 wires together that go strait to the switch?

[@grayfurnaceman]

Yes, for testing only. However, leaving the jumper installed will result in dangerous overheat of the furnace. GFM

[@msj103105]

Good Day I have a furnace that the exhaust fan and blower motor come on, when a call for heat is initiated. I also get a code for pressure switch error. Why would the exhaust and blower come on at the same time Thank you

[@grayfurnaceman]

It may be because of the failure code. Some furnaces turn on those fans to let you know there is a problem. GFM

[@msj103105]

grayfurnaceman thanks For the quick reply, gonna replace the PS its to be faulty, after jumping it out it worked. thanks i always learn from your vids

[@FTGxSoJuFoRcEs]

Thanks Hank Hill 😎

[@mumenrider862]

if it's a goodman, the board is probably bad. If you check the limits and they're good, replace the board with an updated one.

[@joyful4350]

Hello Sir, I just had a blower motor replaced on a 7 year old Carrier 95, but limit switch error code (4 blinking lights)still comes on and burners shut down only to come back on when furnace cools down. Filters fine. Blower fans clean. Could it just be a faulty limit switch or is there something else I should be making sure my HVAC tech should be checking? Thank you

[@grayfurnaceman]

You probably have an air flow problem. Secondary heat exchanger plugged. A/C coil plugged. GFM

[@sergeihanush2262]

I have Westinghouse/Nordyne fg6ra 096c-16b furnace. And my blower could randomly turn on between heat cycles with inducer on together. When i come to the board and see red led light it is constantly blinking. Error coded state that in this situation it is false flame (flame sensor was just replaced) OR Gas Valve relay shorter. I didn't replace yet gas valve because i can't convince myself that problem is actually in gas valve. If someone could help me convince myself that shorted gas valve relay could cause inducer and fan run together randomly between heat cycles? Thank you

[@grayfurnaceman]

A shorted gas valve relay could not, but a failed control board could. GFM

[@sergeihanush2262]

@@grayfurnaceman Thank you. That is my suspect at this moment as well

[@garyduran1]

When the thermostat is off(no call for heat) I hear a fan come on, then off, then on? When i do call for heat everything works fine? Can you help me? thank you

[@grayfurnaceman]

If the unit has a heat operated fan switch, the on and off temps may be too close. If you set them farther apart, it could stop the problem. GFM

[@garyduran1]

Thank you sir, no heat operated fan switch on this unit. In the wee hours of the morning I can hear the little fan turn on, as if I am calling for heat, but then turns off, then on then off? And it does this when the thermostat is on auto and off. Day and night L.P. model 376CAV036075. Is it possible its scencing a propane leak and turns on to clear? I am baffled. Thanks again.

[@grayfurnaceman]

Not a propane problem. That sounds like a thermostat problem. Try bypassing it. GFM

[@garyduran1]

I am just a DIY.. I am not familiar with GFM. I did replace thermostat a few weeks ago with a cheap honeywell one.. maybe i need a better one? thank you.

[@grayfurnaceman]

GFM is short for Grayfurnaceman. If you remove the wires from the thermostat, and and it does not come on at night, the thermostat is the problem. GFM

[@MegaWhitesox05]

old 16 year old tempstar when you first start it shuts off then you started 3 more times then its starts running normal is it the gas valve?

[@grayfurnaceman]

MegaWhitesox05 From what you say I would be looking to clean the flame rod. GFM

[@MegaWhitesox05]

it was changed its new it still does the same thing.

[@grayfurnaceman]

Have you tried bypassing the thermostat? GFM

[@MegaWhitesox05]

no but i will try it thanks

[@pixelbat]

Heat stopped working in my Carrier furnace today. Been trying to figure out what's wrong. My blower runs when I turn it to heat for about a minute, then turns off. Only cold air comes out. The draft inducer is pretty noisy, and I suspect something is wrong at that point in the chain, because it doesn't get to the igniter glowing. I know the igniter works tho, because I ran it through the test cycle by shorting the test terminal with 24v Com and it light up during the test. Any ideas? Would the chain stop if the draft inducer was weak or not working properly? My LED codes are totally normal. Any advise is appreciated! Thanks

[@grayfurnaceman]

I would be looking at pressure switch problems. If you jumper the pressure switch during a trial for ignition, does it come on? GFM

[@pixelbat]

Thank you so much for the advise. I figured it out. It was the draft inducer motor. It was seizing up. I gave it some turns and it started to work again, and everything kicked on. Ordered replacement, so I'm pretty confident that motor is literally on it's last leg. I'm just happy to have heat again. Still cold here in Michigan.

[@solarsynapse]

My blower fan randomly comes on and runs for a short time and then goes off with no call for heat.

[@grayfurnaceman]

Can you give me an approximate age of the furnace? GFM

[@solarsynapse]

Not sure. 2002? It is a Coleman DGAT075BDF that was used a couple of seasons and then sat for years. The mobile home was scrapped and the furnace installed into a 1986 mobile home fall of 2017. For grins I cleaned the flame sensor rod and replaced the board with one from a known working unit. Same thing. My next guess is one or both of the temp switches. Sometimes when it cycles from a call for heat the flame goes out when the blower comes on and then it recycles and works. Haunted.

[@grayfurnaceman]

Could be the whole house fan is coming on. Mobiles of that age do have a fan to bring in outside air periodically. GFM

[@solarsynapse]

Wow, never thought of that. Learn something new every day.

[@lorrainenunnelley2853]

My fan is just running all the time, in the off position and on auto as well, gas furnace. Also my a/c is broken. With a 4 year old this is so frustrating..

[@grayfurnaceman]

A gas furnace will turn on the fan to alert the homeowner that there is a failure in the furnace. Have you checked the error code? There is a light that will blink a code viewed thru a small window in the furnace cover. The key to the code is usually on the inside of one of the covers GFM

[@alisaad-oj9oq]

Lori Nunnelley is

[@speed5763]

you need to do one about the right filter good -better -best TOO thick --less air flow -- MORE PROBLEMS .... I WANT THE BEST---but my 15 year old oil furnace is not getting enough air ---FAN is always running

[@grayfurnaceman]

I have a series in mind and will be getting it out there hopefully soon. GFM

[@MrWaseskwan]

My whirrlyball was on

[@cavibird2005]

Secondary HE Externally or internally plugged up.

[@grayfurnaceman]

That could certainly cause it. Thanks for the thoughts. GFM

[@adambrecker2600]

my furnace fan blows air and no heat also I hear a clicking noise a lot do you know what that noise is??? Thanks.

[@grayfurnaceman]

Gas furnace? GFM

[@adambrecker2600]

It's a Beckett oil burner

[@grayfurnaceman]

I am not sure what the noise is but your burner has probably shut down on flame safety. GFM

[@adambrecker2600]

grayfurnaceman I also pulled out the fuel nozzle electrode mechanism it was all black.

[@grayfurnaceman]

It is normal for the gun assembly to be black from extended use. That does not mean the nozzle is not plugged. When the gun is removed, the assembly should be cleaned and the nozzle should be replaced. GFM

[@x.y.8581]

How do you set the old style (one on left in video) limit switch?

[@grayfurnaceman]

I have a video on that. kzbin.info/www/bejne/h6Grl3maoJVnq5I GFM

[@antoniokristler6973]

Cracked heat exchangers build up heat. Plugged evap coils from sweaty pet hair/dirt/drywall dust. For the love of god if its over 13 check that exchanger, if its a 90 percent unit remove the inducer motor and check for rust by the blower. Plugged secondaries can happen even at 12 years.

[@bigking1954]

Antonio Kristler how to install a switch with a Buss fuse on it to a furnace show how to install a switch with a Buss fuse in it for a furnace

[@edbtzkhud]

99.9 percent of the time it’s a control board. I’ve seen filters that haven’t been changed in more than two years and didn’t have this symptom. Just google the model number pick your part and replace!

[@grayfurnaceman]

that has not been my experience. A continuously running fan could be a stuck limit, rollout switch open, flame failure, or pressure switch problems. The IFC is the absolute last part I would replace. GFM

[@Chiwawaleg]

edbtzkhud youre an idiot

[@bobheck7303]

I agree with leg!

[@jaybeecee1949]

Who the hell keeps their house at 73 degrees? Put on a sweater!

[@ramonaburns605]

brainmatterz screw that mine stays at 75