How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Mark Henley Your Own Question

Mark Henley
Mark Henley, Journeyman Technician
Category: HVAC
Satisfied Customers: 3217
Experience:  UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential
10307865
Type Your HVAC Question Here...
Mark Henley is online now
A new question is answered every 9 seconds

My furnace fan wont shut off automatically. The thermostat

Resolved Question:

My furnace fan won't shut off automatically. The thermostat still turns the heat on and off but the fan doesn't go off when the heat goes off. It's a gas forced air furnace.
Submitted: 5 years ago.
Category: HVAC
Expert:  Kenton Guidry replied 5 years ago.

The fan should run for a short period of time after your gas valve shuts off. Although, it sounds as if your fan never shuts off regardless. Can you confirm that your fan is set to auto on your thermostat for me?

Customer: replied 5 years ago.

There is no auto switch or setting on the thermostat. It's an old Lennox furnace installed when the house was built (1973). The fan has an electric manual switch wlith a fuse so I can turn it off manually but then if the thermostat kicks on the heat and I had turned off the fan manually I have to turn it on manually. The thermostat box has a wheel inside with numbers on it which I think is the amount of time for the heat to run or for the amount of time for the furnace to wait before kicking on the heat when the thermostat is turned up. I had this problem once about three years ago; then again once last month; now this is the third time in the last 8 or 10 days. I had to leave the fan on all night the last time in case the heat kicked on during the night. In the morning when I turned the fan off manually and thn turned it back on the fan stopped and seemed to be reset until today again. The only thing on the outside of the thermostat is a lever which slides left or right to turn the heat up or down.

 

 

Expert:  Kenton Guidry replied 5 years ago.
Do you have a brand and model of the thermostat so I can look it up and see what we are working with?
Customer: replied 5 years ago.

Thanks for your patience. Here's what I found out. the Lennox thermostat has this info on the inside back panel: on the far left the letters FY. then in the middle the numbers T834A 1154 and then on the right the number 2.

 

 

The furnace itself is also a lennox with the following info on the panel inside by the pilot button.

 

Line 1 -- TF555

Line 2 --NNN-NN-NNNN1316

Line 3 -- REG. SET 3.5 IN.

Line 4 -- 25 volt 60HZ, .45A

 

While I was checking for this info I switched the fan to the on position and the fan did NOT start running, so at least tonight it will only kick on when the thermostat kicks the heat on.

 

I'm sorry that if you can figure out what's going on you won't make much on this one for all the time it's taking you. But I do appreciate it. I'm a single senior citizen on very limited income and not qte old enough yet to get Social Security. My retired teacher's pay got battered in the stock market downturn so if I can make the old fossil of a furnace working until I can save enough to get a new one if that's what I need to do that would be great.,

Expert:  Kenton Guidry replied 5 years ago.
I noticed that you said the fan will work when the heat has a call for heat. If your fan does this, what is your concern with your current situation.
Customer: replied 5 years ago.

My concern is that when the heat shuts off the fan does not and the fan will run for hours. i don't know how long because when the fan won't go off I have been shutting it off at the switch and every few hours will turn it on to see if it's still running.

 

I would like to know how to get the fan back in sync with the furnace heat output and would rather not have to have the fan running hours on end when it's not circulating heated air.

 

 

Expert:  Kenton Guidry replied 5 years ago.

I am sorry I am going to opt out and suggest someone to take over. I think they will be able to help you further.

Expert:  Mark Henley replied 5 years ago.

Hi ,

 

this sounds like the fan and limit controller is stuck on. If you open the furnace cover you may find a device like the one in the photo. It may have a cover on it. If you can pull the cover off of it you can turn the dial to shut the fan off. Be careful. Could you check if you have one ?

 

Thanks

 

Mark.

 

graphic

Customer: replied 5 years ago.

It's kind of like the photo. No cover on a dial-like wheel which has a lever that can be moved to different positions on the wheel which are labeld with numbers from .18 to .8.

 

Do those numbers control the amount of time the fan is on and are they parts of an hour or a day?

 

Thanks to Kenton for getting me this far and thanks to you for taking over.

Expert:  Mark Henley replied 5 years ago.

Hi,

 

I'm not familiar with exact numbers but they should correlate to minutes that the fan will run after the gas valve shuts down. If the fan is running right now and the gas valve is off you may be able to tap on that control and get the fan to shut down. Try that,

 

 

Thanks

 

Mark

Customer: replied 5 years ago.

Guess you didn't get my first response to this current response of yours. Got knocked off the Net.

 

 

the fan is not currrently running. when I went to get the model number info on the furnace I switched the fan on and it did not run, though several other times todaky I had switched it on and it started running right away. So I guess it got timed out somehow.

 

I will try what you suggest when and if this happens again, which it probably will. But can you tell me why tapping on the wheel inside the thermostat would shut the fan off?

 

also, when i went to check the inside of the thermostat i noticed that the wheel has two little notches in it, one at .25 and one at .3 which lock the wheel in place when I move the lever. Should one of those positions be used? None of the other numbered positions have notches that lock the wheel into place.

 

Also, would turning the thermostat down while the heat and fan are both on cause the fan to keep running when the heat goes off? That's the only thing I've done that might possibly have some effect. Also, should I as a matter of course avoid changing the temperature selection on the thermostate when the furnace is running and the fan is on?

 

am i correct that turning the fan off manually and leaving it off, like overnight, is a bad idea because the furnace might kick on and not having the fan on then would be a hazard?

Expert:  Mark Henley replied 5 years ago.

Hi,

 

No , we have a misunderstanding the photo I showed you would be of a part in the furnace ( remove cover of furnace ) Now I know what the numbers you were talking about are , they are the anticpator settings in the thermostat.

 

This part is located in the furnace that I am referring to. No need to tap on your thermostat.

 

As far as the temperature settings on the thermostat , no you shouldn't have to avoid changing temperature settings on it at all.

 

Thanks

 

Mark.

Customer: replied 5 years ago.

Yes, I did misunderstand. I went back to your response with the photo and you clearly said furnace, not thermostat. I just removed the plate on the fan box in the furnace. It does not look like the photo you showed me. The box has two chambers -- the bottom chamber connects the wall switch to the furnace; the top chamber connects the furnace to a pair of wires that goes through the wall (and probably connects to the house's electrical system and circuit breaker?).

 

there didn't appear to be any switches or dials, just the wires. There is a cylindrical object about an inch and a half long that's covered in heavy orange paper that has this info in it: SEC 24V 20VA Class 2. Looks like some sort of fuse to me but then what do I know. It doesn't look like something I should be messing with but appears to be held in place on ne side with a set screw.

Expert:  Mark Henley replied 5 years ago.

Hi,

 

Yeah that's the transformer, there is some type of fan limit on the furnace, Lennox did use a few different ones. I may not be able to guide you to it but I am quite sure that is your problem as the symptoms are classic. You may want to invest in a service call as the part will need to be changed anyway. They should have one on their truck.

 

Thanks

 

Mark.

 

 

Customer: replied 5 years ago.

Okay. If you can guide me to it that's all the much more I'll know and be able to watch for when i have the work done.

 

So, guide me to it if you can.

 

Also, please confirm that what I most likely need replaced is a part called a fan limiter. Less likely I'll get ripped off if I know what i need done and what to call it rather than that "thingamabob."

 

Also, I know you can't give me an estimate but can you ballbark the cost of the part and the amount of labor involved, though if it's less than an hour I understand that I'll either have to pay for an hour or a standard "show up" charge. Thanks.

Expert:  Mark Henley replied 5 years ago.

Hi,

 

In general it will be located in the upper part of the furnace and be mounted on the wall that that the burners go into so if you pull the cover off it should be right there in front of you. Lennox also used some that are a different style but they were called the same thing a , fan & limit control.

 

The price could be as much as 150 dollars and it really shouldn't be more than hours labor to put it in complete. It could be a 300 dollar repair.

 

Here is a picture of another Lennox style control.

 

graphic

 

You won't see the probe only the brown part.

 

 

Thanks

 

Mark.

 

 

 

Customer: replied 5 years ago.

Bless your heart! I found it from your description that the heaters go into it. the cover just popped off and the dial is sideways to the first photo you sent but looks pretty much the same.

 

Now that I found it, what should I do to it for right now?

 

Customer: replied 5 years ago.

 

Are you out there? Sent this response some time ago.

 

 

Bless your heart! I found it from your description that the heaters go into it. the cover just popped off and the dial is sideways to the first photo you sent but looks pretty much the same.

 

Now that I found it, what should I do to it for right now?

 

Expert:  Mark Henley replied 5 years ago.

Hi,

 

 

Well , to verify it is the problem all we really have to do is wait until it happens again and just slightly tap on it to shut the blower down. Short of replacing it there is no way to repair it.

 

Thank you

 

Mark.

 

 

Mark Henley, Journeyman Technician
Category: HVAC
Satisfied Customers: 3217
Experience: UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential
Mark Henley and 9 other HVAC Specialists are ready to help you
Customer: replied 5 years ago.

you don't need to "answer" this. I just want to say a million thanks for your expertise and patience.

 

Guess maybe I "unstuck" the fan and limit control when I tapped on it last night because this morning I turned up the thermostat and let it run through several cycles and the fan worked fine.

 

If it sticks again, I'll know what to have repaired.

 

You were just great! I contacted customer service last night to find out how I could pay you a little more as a token of my appreciation. It will be only a token because as far as I'm concerned you and the help you provided are invaluable to people like me. and I can only recognize with praise the inordinant amount of time you spent to help me. I unequivocally and highly recommend you and will give the web site feedback to that effect. Easy to see why you've had a 100% "accept" rate for hundreds of answers.

 

You took away my feeling of helplessness because now I know what the problem is and can discuss repairs intelligently instead of being an ignorant, defenseless customer.

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • You did one super job of explaining to me everything there is to know about this fridge. I'm looking forward to asking you questions in the future. Jimmy Bagley, IA
< Last | Next >
  • You did one super job of explaining to me everything there is to know about this fridge. I'm looking forward to asking you questions in the future. Jimmy Bagley, IA
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
 
 
 

Meet The Experts:

 
 
 
  • gotoman for ac

    HVAC Technician

    Satisfied Customers:

    4657
    51 years of experience install design and repair of all makes and models of AC
< Last | Next >
  • http://ww2.justanswer.com/uploads/SE/ServiceTechRus/2012-6-7_2119_056.64x64.JPG gotoman for ac's Avatar

    gotoman for ac

    HVAC Technician

    Satisfied Customers:

    4657
    51 years of experience install design and repair of all makes and models of AC
  • http://ww2.justanswer.com/uploads/AL/alumalite/2012-5-10_234018_shutterstock506249951forJA500.64x64.jpg Phil's Avatar

    Phil

    Mechanical Engineer

    Satisfied Customers:

    3888
    Retired HVAC/ Electrical & Boiler contractor. Industrial
  • http://ww2.justanswer.com/uploads/skibum0101/2008-12-16_015819_just_answer.jpg Rick Mather's Avatar

    Rick Mather

    HVAC Technician

    Satisfied Customers:

    3132
    35 years experience, HVAC
  • http://ww2.justanswer.com/uploads/RY/Rygis20/2011-5-7_3143_DSC5324.64x64.JPG Matthew's Avatar

    Matthew

    HVAC Technician

    Satisfied Customers:

    1994
    14 years experience in the HVAC field of service, installation, Manual J & D calculations
  • http://ww2.justanswer.com/uploads/KE/kentguidry/2011-9-26_214316_0059.64x64.jpg Kenton Guidry's Avatar

    Kenton Guidry

    HVAC Technician

    Satisfied Customers:

    962
    12 years install/service experience.
  • http://ww2.justanswer.com/uploads/solarman1947/2009-12-13_223915_phpkKBcXq_c2PM.jpg Rick Ridley's Avatar

    Rick Ridley

    UK Heating Engineer

    Satisfied Customers:

    871
    Retired But have had 30 years on the tools, Ex CORGI
  • http://ww2.justanswer.com/uploads/Ironheadfan/2009-12-18_222416_pump_005.jpg Tom's Avatar

    Tom

    HVAC Technician

    Satisfied Customers:

    770
    16+yrs HVAC/R service. Residential Commerical Industrial
 
 
 

Related HVAC Questions

Chat Now With A HVAC Technician
Mark Henley
Mark Henley
HVAC Controls DDC
3214 Satisfied Customers
UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential