How to adjust the Honeywell fan and limit switch

[@stevegasparino1]

Just like to tell you youre invaluable to people and are appreciated. I bought the family home in 2016, that was built in 1955. It heats with a Majestic fuel oil furnace that has been maintained meticulousy by my uncle, who built the house. Your videos have helped me keep this old furnace running and performing like new. I just cured a problem watching the fan limit control setting video. perfect remedy, cycles as it should now. Again, Thank you so much!!! Steve Gasparino Muncie Indiana

[@grayfurnaceman]

Glad I could help. GFM

[@nttrung30]

Purchased: August 2023 - still works GREAT!I kzbin.infoUgkxxsUnXhGsSJLim_XnMHyQK0u3XVaW-CGn live in a studio and during the summer it gets scorching hot - really old building with no ac units. I can’t express how EASY it was to install. This unit has been a life savior during the summer and some days during other seasons where it can still be a bit warm at night. In this small place is my friend, a husky, poodle mix and myself. We need AC - lolI don’t use the dehumidifier option - I’m not sure if it will leak in my house, since I did not install the small draining hose that came with it. May look into it late but I don’t worry about much humidity in the apartment. I don’t understand why the negative reviews since all things mentioned, I personally did not find issues with. Definitely worth it!

[@MrTurnone]

This video is still helping people after all these years...thank you very much!

[@grayfurnaceman]

Welcome GFM

[@randybell3]

I am a young HVAC tech and I'm learning new tricks from you all the time by watching your videos, thank you very much for all the information you have put out in all of your videos.

[@halekus7664]

*Works great **Fastly.Cool** compact and Easy to install*

[@Romantico1962]

Yes this video still helping me after all this years to figure out what was this dial. Thanks for the information.

[@robertsmith7637]

You are a big help. I have a 1970 Luxaire model up here in Detroit still getting it done. Thanks for all of the videos. 👍💪🇺🇸💪👍

[@glasser2819]

Thank you GrayFurnaceMan. You"re a true master at empowering others by explaining tricky systems in simple ways

[@grayfurnaceman]

Merry Christmas GFM

[@brianmcdonald6991]

Good video, helped fix my brothers furnace after we installed a new limit switch. It was right on and the furnace works great now. Thank you

[@ChevySS1968]

Excellent video. Very informative. Loved the way you sped up the rotation of the dial, that really helped demonstrate short-cycling....... Nice work!

[@thefireman2854]

Thank you, this helped me a lot. My fan was staying on. After your videos, I looked at my limiter switch and the settings were 100 to turn on and way down to 50 to turn off. Have no idea how they were set that way. I moved them to 130-140 and 100. workes well now. Much appreciated.

[@woodrage1]

Holy sh!t, you explained everything and didn't blab on and on or say "Ahhhhhhhh" 400 times like other vids I've seen explaining things on youtube. Bravo, this is just what I needed. I'm working on an add on wood furnace and fan runs forever with no heat because the open on the thermodisc was 90 degrees. It's just making the meter spin. Looking for a thermodisc replacement with 130 closed and 100 open. A fan limit switch will probably end up being my fix and thanks to you I know how to set one properly.

[@grayfurnaceman]

Thanks for the support. GFM

[@woodrage1]

Seems to be working, house is hot and fan only running half the time. Have it set to a big swing because it's wood and heats up fast. See if power consumption drops over the next week or two.

[@knight0334]

Thank you!! I have an old ass Ruud furnace, which gives me yearly problems. This year was the fan limit switch and relay. The wire nut from the 120vac side of limit switch to relay came apart behind the 4x4 box, shorting against the relay and taking out the fan limit switch with it. I bought a new fan limit switch, relay, and had to so some rewiring in the furnace - but she is up and running again. This event also gave me time to run new 5 wire thermostat wire and put in a new WIFI thermostat unit while things were down. The old owner had a Honeywell wiresaver in the loop which kinda limited my fan operation. For $100 switch, $10 relay, $30 of 5-wire, and a $50 thermostat - I think I made out over what having a heating/cooling tech come do it.

[@mikekiefer3269]

this is my first comment on your tube ever you just saved my ass with this my furnice I installed was short cycling durning a cold snap -16 degrees figured out something was wrong after temp in house were below 60 my fan off and on points on my furnice were so close together that it would heat up fan would kick on and temp would drop so fast it wouldn't stay on for more than a min now all good thanks!!!

[@grayfurnaceman]

+Mike Kiefer Welcome GFM

[@glasser2819]

Mike Kiefer ... so your burner limit was set too low, right? > ~180F

[@erickhorning823]

Thank you that was very helpful video! Mine was set way wrong. I don't know how it moved itself or what or if it was always set wrong but my fan on was way too close to the 200. So the fire was going almost all the way up till 200 before the fan kick on and then the high limit 200 would shut the fire back off. Now after watching your video seems to be working properly thank you!

[@MontyWalls]

thank you for your help, local company wanted to replace the heater. Your tip solved the problem we where having.... saved a ton of money. THANK YOU!!!

[@grayfurnaceman]

Welcome GFM

[@robertfleming2614]

This is about the same honeywell limit that are on a lot of the oil furnaces im used to working on,ive had to change just a few, they are very reliable,thanks again

[@rodgraff1782]

These Honeywell fan and limit controls are the sturdiest, most dependable controls I’ve seen. They make a version that has a 24 volt heater, we used to call a sure start, to help bring on the fan, and keep it from short cycling. This type was mostly used on downflow and horizontal furnaces, because they were located on the furnace, where they didn’t sense accurate temperature until the fan started. These controls had 6 connections. Camstat made a plastic version that didn’t use the helix by metal, and they were much lower quality. They both came in different lengths

[@grayfurnaceman]

I have not seen the heater version for a number of years. GFM

[@mariemackey6132]

I'm a late comer but your video is awesome. Thank for the help. 👌

[@senecadaze]

thanks for the video very helpful for working on my heil furnace. Also i like how you take time to answer all questions, you save people boat loads of money.

[@grayfurnaceman]

Thanks for the support. GFM

[@christopherpenny6216]

Thank you very much. Now I understand my mystical Old furnace a little bit

[@Primel451]

Thank you for posting this. I just installed a furnace and was wondering what the hell the setting should be.

[@royjohnsen7574]

My fan was cycling on independent of the theremostat, it turned out to be the fan on/off settings were too close together as you stated in the video. Thank you for posting this!

[@grayfurnaceman]

Roy Johnsen Welcome. GFM

[@grayfurnaceman]

I would set the "on" at 140 degrees. The "off" seems a little low but unless the fan comes on in the summer and does not shut off, leave it alone. Hope this helps. GFM

[@grayfurnaceman]

I reset the channel settings so it should work. Are you doing wood projects? If so, the heat exchanger could be plugged with burned sawdust. Only other possibility would be a negative pressure in the structure such as exhaust fans etc. GFM

[@grayfurnaceman]

It could be the attic temp. Gosh, I hate to set it higher than 150. The limit probably is set to 180 or 200 so that's pretty close. Are the turbine fans operated by wind? If so, a good idea would be to install a powered attic fan. You would also reduce cooling costs. Hope this helps. GFM

[@whattodo5416]

Dear GFM, I think we can use a digital thermostat no problem. Tommorow I have to do wiring on something like this. I will use the W and common from a digital thermostat, and connect it across gas valve . Then just wire the rest of it in the way we normally do with the fan limit switch. The thermostat digital or mechanical, just is a switch making gas valve work..

[@coolbluelights]

Thanks for this video. Had the one on my furnace set wrong for years and it would short cycle a couple times after the burner shut off

[@cookingwithcuyandotherfuns6238]

This is great.....our furnace is short cycling. About every 5th run. Thank you. Going to try 100F and 130F when I get home.

[@rodgraff1782]

I’ve had to go on at 130 and off at 90., at times. They do make a heat assisted version that will eliminate any short cycling problems.

[@tjhooker18]

Saved me twice in 2 weeks Gray! thanks man!

[@larryw7905]

Thank you for the video!!! I learned a lot from your post. It also saved me money and time!!!

[@SuperSteelerFreak79]

Good video. Great idea speeding up the short cycle. Thanks.

[@speedtekauto]

Good videos and very understanding. Thank you. I'm glad I found this one.

[@grayfurnaceman]

speedtekauto WelcomeGFM

[@RobbieBobbie98]

This is excellent advice. The best one I’ve seen. I’m having trouble using my blower fan to circulate wood heat so the fan will automatically shut off at my preset temperature. Nobody knows how to do this and I can run my blower fan without using gas but it won’t automatically shut off, it gets too hot and I have to manually turn it off. Any suggestions?

[@grayfurnaceman]

Watch the burners when they operate to see if they rollout. May take a couple of minutes. Painting is the worst for these furnaces as they draw air from inside the structure. You can try replacing the wires but be careful! GFM

[@grayfurnaceman]

This one could be bad. Is it a GE vintage 1970s or early 1980s? The burned wires indicate probable flame rollout. This can be very dangerous. If you can send pics in a video response that could help. Let me know. GFM

[@grayfurnaceman]

It would always be best to replace the fuse like for like. However, the fuse is generally matched to the wire size which would probably be #14 or 15 amps. To be safe I would not leave it with the 15. The rail burns are probably normal from the flame spreader. The short cycling is probably thermostat anticipator. Check out the "thermostat anticipator" in the search engine at the channel for instructions on how to adjust. GFM

[@Lazyguy2112]

your awesome gray man. thanks for sharing your knowledge.

[@grayfurnaceman]

Merry Christmas GFM

[@akbaxb165]

Thanks for posting the video. My Lennox furnace is about 23 years old. Last maintenance service was done in 2012. The Honeywell Fan Limit Switch is set up at 100/150/200. I like to keep the furnace motor on all the time - to circulate the air around the house by setting the fan option on the house thermostat in the living room to ON rather than Auto (Note: the Limit Switch Unit button is still on AUTO rather than Manual). Can I adjust the 100/150 numbers so that the blower comes on early and keeps going longer even when the burner flames are no longer ignited. That way, I can put the fan option on the thermostat in the living room to AUTO option rather than ON all the time. Also, how long can a blower motor last if the furnace is properly maintained (regular filter change/motor lubrication etc)? So far the original motor is still running. Thanks for your help and advice in this matter.

[@glasser2819]

akbaxb165 don't overlook the blower run capacitor. The value changes little by little as they age... eventually the windings are so out of balance that the insulation can cook or boil of lubricant from sleeve bearings. The run cap is used to create an artificial 2nd phase with voltage shifted at 180°. The value must match precisely the windings.

[@majorburke9735]

Hi! My replacement combo fan limit switch has no LIMITERS. My old one limited the high dial to 175-degrees. But I can put my new switch dials, left (lowest of the three), middle and right (highest), anywhere from 50-250. I set the dials as close as I could to the old settings-100, 140, 175. You said it’s best to set the low at 100 👍, but is there a danger to setting the high to high? I won’t do anything different until I hear back from you.

[@grayfurnaceman]

My guess is the temp on and off is too close together. Go to 140 or 150. If still no luck, you can try a shield below the sensor. GFM

[@eric321ification]

This helped provide longer cycles. Thanks

[@grayfurnaceman]

Welcome GFM

[@rbevans4581]

Thank you very much for your time with this. My fan is not shutting off. I have the limit at 200 and the fan range at 80 to 110. Once the dial appears to have stopped turning and the fan continues running if I lightly tap the furnace metal next to where the switch is mounted it turns and shuts off. Does this require a new switch or is there something I can do to lube the dial shaft? Graphite?

[@grayfurnaceman]

Usually if they stick like that, the best thing to do is replace. GFM

[@TheFirstgoldking]

My furnace arrived in 7 boxs with a note saying good luck...im a good mechanic..after watching your vid I ck this fan switch it was set 100 130 forced air..the baseboard heat has never been hot just tepid I live in fairbanks alaska Brrrr!! the thermo couple rod was touching the top edge of the outer burner box..that could explain why the fan came on after shut down.that install was my ignorance. hope this correction reduces my $6000 a yr home heating bill any amount.. Thanks again

[@ffangoria]

Thanks for the help. I'm going to upload another photo for you. I replaced the wires and the delay fuse. It had an 10amp and I could only find a 15 amp, will this hurt? Replacing the wires and fuse got the system back up and running but there is still a problem. You will see in the pic the burn marks on the rail outside the burners. Ran system 15 minutes, didn't see any rollback of the flame. Burner shut down several times before reaching thermostat temp, this is probably normal. Next post

[@williamstone6818]

You da man!!!! My off limiter was set too low

[@dansclassicsandcustoms]

You say I Shouldn't put it below 100*, but if I don't set it to 90* to cool down, the fan kicks on again from the leftover heat in the exchanger. It's already set to come on at 140*. Do I need to set it higher to come on at 145* then?

[@dansclassicsandcustoms]

Edit: I have moved the indicator to 145* and it's still kicking the fan on again after it sits for 2 minutes...I discovered that I can solve the issue by either cranking it up to come on at 155* off at 90*. Which is better?

[@grayfurnaceman]

@@dansclassicsandcustoms You can certainly set the off temp to 90F. The only issue is it may stay on if the ambient duct temp is above 90F. GFM

[@ffangoria]

Hi furnaceman, thanks for the vids. I have a gas furnace in my garage and I tyied to turn it on the other day and it didn't work. I discovered the wires from the fan and limit switch were burned to a crisp. Any idea why this happedned. Can I just replace the 3 wires or do I need a new switch? Thanks

[@grayfurnaceman]

Yes, they are for mechanical only. The problem may be location. GFM

[@MrGeoffois]

Great video. I just sent you a question to one of your other videos and I'm wondering if this is the problem that the fan switch isn't set right but the problem is that the fan comes on and shuts off after a couple seconds but only shuts off for a split second then comes on longer and long then stays on. Maybe the settings are right on top of each other till it gets hot enough to drive the dial past those settings?

[@holymolybullykennels900]

OK I'm going to check that out today with a better and get back to you on diagnoses.

[@mwngw]

Excellent demo. My symptom on my Duomatic Olson with a Honeywell Fan Limit Combo switch is the burner lighting, blower comes on for 2 1/2 minutes, then burner shuts off along with blower...and in about 2-3 minutes recycles and keep repeating the cycle. The fan switch is original. So basically, the furnace heats for 2 1/2 minutes, shuts off, rests for 2-3 minutes, then repeats. Any ideas?

[@grayfurnaceman]

You can jumper the thermostat connections to be sure the thermostat is not short cycling. GFM

[@ffangoria]

Spray painted some house doors. Furnace is boxed in with filters on the intake. Should I replace the wires and see if it works. I don't use it much just once in a while. Thanks

[@amird5559]

My furnace shuts off at the appropriate temperature. But the unit keeps blowing cool air for 20 minutes after the furnace or heating shuts off. I know that the fan needs to blow off all the hot air into the house but 20 minutes is a long time. Do I have to readjust the fan limit switch?

[@grayfurnaceman]

If the fan switch is adjustable, I would say so. GFM

[@x.y.8581]

Obviously yes - try that and let us know if that fixes your problem.

[@ffangoria]

I posted pic as video, I guess you need to approve it? It an Air Ease furnace I think, thats what it says on front cover. Has a pilot light. I ran it for about 2 weeks this winter to do a project. Forgot to turn it off, no big deal, just wasn't in garage. It was running so I realized I'd left it on. Turned off and turned power off. Would not come on last week and this is what I found. Not sure how it was running before I shut it down? Thanks for any help.

[@thevintagefetcher]

thank you for a very helpful video series! here's my question: when my filters are dirty, i can run at these settings. (the 100 and 130..) but with new clean filters, at these settings the blower will kick on and then off fairly quickly. it only stays off for a second or two and then with a 'lurch' will turn back on again. if i lower the temps to 90 and 130, the air just doesnt seem very hot. any suggestions?

[@grayfurnaceman]

That is a common problem when the temps are too close. I would set the on temp for 140 and leave off at 100.

[@thevintagefetcher]

ill give it a try and let you know. thank you very much!

[@thevintagefetcher]

grayfurnaceman well, now it appears to be intermittent. it didnt do it earlier today, but i just heard it again. it stops for a brief second (not even long enough for the blower to stop turning) and then kicks on again. very strange.

[@grayfurnaceman]

Some of these switches have an electric heater built into the switch. If the heater is burned out it will short cycle. It should be located at the center of the black portion of the switch with 2 wires mounted there. I will do a video about that as soon as I find one. Also some of these switches had an air dam below the element. If that was removed, it would cause that. GFM

[@ffangoria]

Not sure about why I'm having trouble with this post. Furnace keeps coming on even when up to temp. Only after I lowered thermostat a few degrees would it cycle off. Fan limit is set at about 110 and 150. Not sure when or why there are burns on that rail, but seems at some point the flame did rollback. Since the system seems to not want to shut down could this be why the wires got burned? Looks like a Johnson furnace. Thanks for any help

[@jdmferio08]

Would bad settings cause the pil furnace to always shut off when getting to got and put it in reset mode ? I'm having issues with my thermopride. I can't set my thermostate below 70 in my older 1970s home cause it shuts off and needs manually reset.

[@grayfurnaceman]

No. If you must reset the cad cell relay, you have a problem either with flame shutdown during operation or the cad cell is no seeing the flame. Start with cleaning the cad cell. GFM

[@robertweeks1171]

I set my temp range on my old honeywell to cut the fan on at 130 degrees, and cutout fan at 90 degrees. However this is what is happening. Furnace starts heats up to 130, and the fan cycles, but it quickly lowers in temp pass the cutout point and shuts the blower fan off. Would you think this would be a bad limit switch, just by how it is acting.

[@vdeblois1352]

Hello 😊 .. i saw on another video that (for the white Rodgers) the white plastic dot on top (under the manual auto switch) should be aligned to the room temp when it reaches it.. if thats true mine is about 40° off! .. can you confirm this?

[@vdeblois1352]

It's hard to find info on calibration.. I understand it is done in factory.. but can you recalibrate, or should I change it altogether? A few years ago I would've but these things are suddenly very expensive!

[@grayfurnaceman]

I have never heard of that one. GFM@@vdeblois1352

[@vdeblois1352]

@@grayfurnaceman thanks 👍🏼

[@gregpatey6355]

very helpful video in understanding this type of limit switch.... I have watched both videos about how the limit switch works and how to adjust it, but it still doesnt answer the question I have.... the oil burner heater in my shop keeps shutting OFF because the fan isnt coming on soon enough (if I rotate the switch just slightly by hand so the "on" peg passes the mark, the fan comes on and the burner remains running (or if I turn the fan on with the "manual" switch the burner remains running)...... after lowering the "on" peg, it still doesnt reach the on position before the burner reaches the temp at which is shuts off by default (then the reset button needs to be held in for it to retry to start the burner).... I have had furnace techs here to tune up the furnace, and after it gets started and running, it works flawlessly, but NOT until the fan comes on, and so they seem to always miss fixing the problem... what could be the cause of the unit "timing out" because the fan doesnt come on sooner, as it should?... currently, the "on" peg is set about the halfway mark in the slot and the "off" peg is about 3 marks lower (almost at the end of the slot) what would be a better or modern type of switch to use in place of this one?.... thank you

[@grayfurnaceman]

There is something inconsistent here. Is the burner shutting of on flame failure? GFM

[@gregpatey6355]

@@grayfurnaceman what is happening exactly is, when it is cold and the furnace is turned on, the pump and combustion blower will run about 20 seconds before ignition. it ignites quickly and will then run and heat up the combustion chamber.... after it heats up (about 90 seconds or so), the blower fan fails to come on in time to keep the combustion chamber from overheating, and so the burner will be shut off... (apparently by a signal from the overheat thermostat withing the combustion chamber?)..... when I manually start the blower fan about 20-30 seconds after the burner ignites, it will run flawlessly (burner and blower fan will cycle on and off as the shop temperature demands) the rest of the day... this only happens when its cold on the first start up of the day...

[@electriccar3253]

​@@gregpatey6355 There could be a crack in the heat exchanger feeding hot gasses onto the sensor. You may also be over fired. Too large a nozzle. Just a couple of thoughts. GFM

[@x.y.8581]

Try replacing the limit switch?

[@CranialAccess]

I have a Miller Oil furnace. The burner goes on for a bit then shuts down the fan comes on after a few minutes starts blowing and then the burner starts up again. I have a sense that my fan limit switch is set incorrectly?

[@grayfurnaceman]

I would jumper out the thermostat. If it continues to short cycle, you could have a fan limit problem. GFM

[@mwngw]

Are those connections on the switch via spade connectors?

[@franklincycles7462]

I adjusted it like in this video and my fan does not turn off, it continuously goes. the thermostat and button on the limit switch is set to auto and, the fan switch on the furnace is is turned off. would this be a defective switch? thanks

[@grayfurnaceman]

I would say it is out of calibration and must be replaced. GFM

[@franklincycles7462]

@@grayfurnaceman thanks for the quick reply

[@purplefishgirl3719]

Hi there thanks so much for having all this great videos 😎 I just installed at limit switch and I have it set at 100 140 200 I want to make it so the blower comes on right after the flame starts what number would I use thanks so much ⚒

[@grayfurnaceman]

For it to work properly, you will need the burner on for 30 to 45 seconds before the fan comes on. Your settings are what I would do as an initial setting. Setting the on below 140 may cause the fan to short cycle. GFM

[@purplefishgirl3719]

Thanks so much for your help I timed it and it does come on 35 seconds after the burner starts. So by watching your videos I did it the right way keep up the great videos

[@x.y.8581]

The fan should run sometime (30-90sec) after the burner comes on - you don't want cool or cold air blowing from the ducts (unless its A/C functioning).

[@boboala1]

Wouldn't a vintage Honeywell limit switch have a 4-digit number labeled as the model #? I'm not sure what you called it at the end of the video...? A friend of mine just got an old Monarch 'Add-A-Furnace' outdoor wood furnace with test date imprint 1978 and a Honeywell 8049 (?) I didn't have my phone or a camera with me, and it was getting dark & box kinda dirty, so I may have confused a '9' for what should've been a 6, as in 8046.

[@Angeladvntg]

THANK YOU SO MUCH FOR THIS!!

[@grayfurnaceman]

Quite welcome. GFM

[@CL-ty6wp]

I have an old oil furnace, it hits the limit ever 7ish mins and turns off only the burner for 2 or 3 mins than fires back up. Is this normal or a bad thing? Aka overheating. New filters, door open to filters, no blockage. Seems fine to me since the house heats the same but burner is off almost half heat cycle. So im using less oil vs burning the whole cycle. Im just wondering if this isnt correct, will the switch wear prematurely. The blower has no control board to be seen but above the furnace there is a redbox with a blk button 'thermal cutoff switch' no adjustments.

[@grayfurnaceman]

You are probably overfired. Smaller nozzle may help. GFM

[@CL-ty6wp]

@@grayfurnaceman I was leaning towards that as a fix and might get a gauge to check/tune pump pressure because I am at the right size @ .85 according to silver plaque. It does have a newer replacement suntec pump that i'm thinking might be too high psi for my ancient burner. Thank you very much for all the videos and taking time to reply.

[@corneater69]

AT the end you say the fan should not come after a cycle, My oil furnace occasionally the burner will come on and run then turn off and about a minute later the fan will come on for a while. I have watched the fan and limit switch cycle as you have indicated it should work. Should my furnace function this way?

[@grayfurnaceman]

No. I would separate the on and off temps a little farther. Be sure the power is off when you do this. Hope this helps. GFM

[@VideoGuy84]

I have one of these limit switches and the blower will cycle on and off several times after the burner has shut down, it does this regardless of where I set the FAN OFF peg. Also the dial never seems to rotate below 100 degrees even if the furnace has been off for a long time. I’m guessing the spring is probably completely out of whack?

[@grayfurnaceman]

Its probably toast. Replace it. GFM

[@Liberty309]

My furnace has always worked fine, never changed any of the limit switch setting. I turned it on yesterday to test for the season. It turns on and blows heat fine but the blower shuts off before the desired room temperature setting on the thermostat but the burners are still going. The blower kicks on again for about a minute and then shuts off again. I watched the limit switch and It seems as though it is cooling off too fast to bring it back to the off position. What do you think?

[@grayfurnaceman]

Two issues I can think of. The structure is very cold so the return air is coming back at less than 60F. The switch is failing. GFM

[@Liberty309]

What did you mean in the video when you said you had it set to 4x's the normal speed ?

[@Liberty309]

@@grayfurnaceman Thanks for your advice. It was the switch going bad. I put in a new one today and it's working perfectly normal again. :-)

[@frankellis1980]

My furnace turns on, gets to temp, but blower doesn't turn on. When max temp is reached, system shuts down. I tried pushing the manual fan control on and fan does not come on. Would this indicate a bad limit switch?

[@grayfurnaceman]

Either your fan switch has failed or the fan motor has failed. GFM

[@95ZR580]

Hey, do I need to adjust these for my central ac? The fan will only run when in manual mode.

[@grayfurnaceman]

The heat operated fan switch is only used in the heat mode. GFM

[@dianewallace6017]

This looks exactly like the thermostat to the wood furnace I am using in the house I am renting. The settings are at 110 degrees and 150 degrees. The fan is continuous starting at 75 degrees in the house and only shuts off after the wood turns to embers. The house temperature usually reaches 90 degrees, but the wood burns quickly (even with damper shut) within an hour or two. I have not been able to sleep through night because the wood (2/3 - 3/4) full will burn up within 3-4 hours. I attempted to move the pointers to 100 and 130 but they would not budge. Please advise!

[@grayfurnaceman]

***** The setting is not the problem. Once the furnace is loaded, the fan will be on until fire is essentially out. The problem you are seeing is endemic to wood heat. All I can tell you is the wood species does make a difference for holding fire for long periods. Depending on where you live, red fir is a fire holding wood. Also hickory will hold a fire. Hope this helps. GFM

[@dianewallace6017]

Thank you for your response. I am new to wood burning so I had no clue what kind of firewood to look for. I will keep this in mind next time around!

[@samanthaweiss2243]

It seems my fan & limit switch is working, but I was having that issue where it was cycling on and off about 3 times before staying on late last winter, so while getting my furnace fired up today for the fall season, we tweaked the dial, and now the fan won't kick on at all. Can it be coincidence that the fan died right then and there? The fan motor is relatively new; only 1 and a half winters. The fan & limit switch is on it's 7th winter. I have it off at about 100, and on at about 150.

[@samanthaweiss2243]

Also, the fan did work once today, when everything was initially fired up, but it did that on/off thing so that is when we tweaked it. Now no fan. :(

[@grayfurnaceman]

If you did not hold down the dial when adjusting, you may have damaged it. GFM

[@FishOnIsMyHandle]

Our Lennox Pulse G14 only runs properly when the thermostat setting is on "FAN" AND NOT ON "AUTO." (When set on "AUTO," the fan usually does not come on.) Is it okay to run it with the thermostat set on "FAN" all the time? Could this be due to a bad thermostat, or bad Fan Limit Control Switch ? THANK YOU

[@grayfurnaceman]

It will work ok with the fan to the on position. The fan switch has probably failed. GFM

[@FishOnIsMyHandle]

@@grayfurnaceman Thank You!!

[@WaynesWorldStudio]

Thank you for the video with great informations, I have an old Lennox G8-105-1 and couldn't find any schematic or manual online, hope you can help. After installed a new Fan limit controllers, my furnace will not starts but when I pull manual fan switch the fan will comes on, this does show I have power from the breaker panel. The old fan controller was working before, just the button was broken so I went replaced with a new unit. I did remove the jumper from the new unit to copy the same unit; I took apart the old unit and there is no jumper. Anyhow, the pilot light stays on but the thermostat set to high temp will not trigger the furnace to come on. I do have the Nest thermostat which states I have NO voltage power to the thermostat since I can't find any schematic out there I wonder if you have any great suggestions? Thank you so much.

[@grayfurnaceman]

Are you sure you have low voltage? GFM

[@WaynesWorldStudio]

Thank you for the reply. The Nest thermostat indicates I have no voltage then I reinstalled my old thermostat and turned on high temp, nothing came on. Wish I can find a schematic diagram for this old furnace.

[@jenoakes6639]

have u replaced the thermostat

[@WaynesWorldStudio]

At first I have removed the jumper switch of the fan limit controller but after fighting to get the furnace to fire up I hire the furnace technician. He came by and putted a jumper into the fan limit controller and now working. Have you replaced your fan limit controller with a new unit?

[@neillefebvre9494]

How to wire a limit switch properly. I have a furnace they unhook everything and cant fined proper schematic.

[@x.y.8581]

You do not show exactly the procedure to adjust the settings. In the comments you say something about "pushing the wheel in" - can you please explain this maybe in another video? Also, please explain "DO NOT ROTATE - HOLD DIAL WHEN SETTING POINTERS"

[@grayfurnaceman]

If you press the dial in, it locks the dial so you can move the pointers without damaging the bimetal sensor. Will consider a video on that. GFM

[@x.y.8581]

Well, maybe I damaged it because the furnace runs all screwy now - fan and burner on & off running quite erratically. Do I need to replace the switch? If so, is there a better design to replace it with? BTW, what's happened with oil burning space heaters? Are they no longer available as I can't seem to find any?

[@grayfurnaceman]

You probably will have to replace it. Their efficiency is quite low, so they have pretty much disappeared. GFM

[@x.y.8581]

Actually, I just kept adjusting (tempted to say "fiddling with" - lol) it and it seems to finally be running ok now. Thanks.

[@fatcat5231]

I thought this may be my issue, but what is happening with our furnace is that the gas keeps kicking on and off until the set temp is reached, then the fan kicks on. The flame is not continuous. Should the gas kick on and off during the cycle of heating up, or should the flames be continuous until the set temp is reached?

[@Denniss7420]

continuous

[@blackopal3138]

Hello Furnaceman, Can I ask you a couple quick questions? Scenario - Furnace was working fine, but very noisy. I took it apart to clean it. Found half a bearing on one side so replaced them, vacuumed, jigalooed everything, put a new belt. 1. Tabs are in same spot, but the 'ON' tab started malfunctioning, as in it hits it turns on, but when the dial starts going back the other way it clicks off immediately from hitting the 'ON' tab again. Is that a sign of a faulty switch?? 2. The ones you work on in your videos don't have a manual/auto button, that I can see, which mine does. If that tab breaks and comes out is there anyway to fix it? or bypass it and just leave it on auto? (I think there is no connection with the button gone so auto doesn't work, just manual when I jam the broken button back in.) Thanks, any help is very appreciated.

[@mk3busterlowhar12]

My furnace shuts on and off. I have cleaned the sensor rod, thoroughly. Intake and exhaust ports are clean. New thermostat. 9 out 10 it's the flame rod. What am I missing.??? S something simple? Need some help. Thanks!!!

[@glasser2819]

Mk3buster Lowhar : this sounds normal. Cycling between set points is what furnaces are designed to do: Heat On > Fan On > Heat Off/On > Fan Off, end of call for heat.

[@qussayali3401]

Hello sir Is there a reason why this fan and limit switch would overheat and meltdown the inside ??

[@grayfurnaceman]

I would be checking the heat exchanger for cracks. You could be getting hot gasses contacting the fan switch. This is a dangerous condition. You could be getting poisonous CO gas into the structure. GFM

[@AZTech25]

hey grayfurnaceman i have the same switch in a dulamatic olsen ultramax 90 series im reaching my 200 degree high temp limit before the temp is met on themostat. do you think that i have a issue with my duct work not pushing enough air out the vents??? i have a end cap on on of the holes on the furnice i took that off now blowing warm air into the basement and it does not reach it limit anymore? is 200 degrees ok for a high limit gas cut off or can i push it to 220 or so

[@grayfurnaceman]

adam Z 200 degrees is the highest temp. Look for dirty filter, dirty blower wheel or ductwork blockages. Hope this helps. GFM

[@amtpdb1]

I just replace my fan control with a universal as the magic chef isn't available. The burner comes on and then after a minute shuts off and then the fan comes on and turns off in a minute then does it again. the house has a burnt smell like the first time turned on in a year. set for 90 and no one can tell me how to set the differential as my old one did not have this feature. can you help me with this. thanks.

[@grayfurnaceman]

If your off temp is set at 90F, the on temp should be about 130F for a 40F differential. GFM

[@ashleybravo5786]

What does it mean when the furnace kicks in then the blower and the dial keeps going up all the way to 200 and shutting off? This happens everytime

[@grayfurnaceman]

+Ashley Bravo You have low airflow. Plugged filter, dirty blower etc. GFM

[@ffangoria]

Thanks, I have a digital thermostat. The vids look like there for a mechanical type?

[@DeutschDrahthaarKY]

What does it mean when the blower runs a normal cycle the shuts off and starts up again maybe 1 minute later only to blow for 30 seconds? Does this every second cycle.

[@grayfurnaceman]

The furnace heat exchanger has not cleared the heat. Try setting the on and off temps a little wider apart. GFM

[@x.y.8581]

When GFM gives you a solution, please have the courtesy to reply if it fixes it or not.

[@upurnose46]

Hey gfm, at the end of the video you talked about the fan coming on after the cycle ends because of heat in the heat exchanger. I am having this problem. Is it a simple adjustment or is my furnace not burning correctly and needs servicing? Thank you

[@grayfurnaceman]

+upurnose46 The "on" and "off" positions need to be farther apart. Usually, this means increasing the "on" temperature. Hope this helps. GFM

[@upurnose46]

+grayfurnaceman My fan settings are Fan OFF-95 Fan On-140 Limit-170. Would this indicate a clogged or bad heat exchanger?

[@grayfurnaceman]

+upurnose46 The switch may be failing. GFM

[@aarondostou3888]

So no matter my fan on and off adjustments, the fan keeps short cycling. Any solutions please

[@grayfurnaceman]

What is your return air temp? GFM

[@aarondostou3888]

@@grayfurnaceman its on a wood furnace so i don’t know . The thermostat is set to on at 130 and off at 100 . It cycles the fan on for 30 seconds then stops constantly

[@aarondostou3888]

@@grayfurnaceman im assuming return air would be room temp seeing part of my ducts vacuum in the homes air and the other ducts expulse hot air

[@grayfurnaceman]

Try on at 150 and off at 100 GFM@@aarondostou3888

[@dennisnoone7427]

GFM, can you replace a fixed fan limit switch (115F-20) with an adjustable one? i got M1S furnace in my rental home and it cycles once or twice after shutting down, i checked air flow and everything is with-in a range, i mostly work on hp and ac and didnt have any hands on exp. with furnaces thanks Dennis

[@grayfurnaceman]

+Dennis No-one There are adjustable fan switches that might fit in your furnace. I would check with a heating contractor. Hope this helps. GFM

[@dennisnoone7427]

the tech support said use the oem fixed fan limit switch, also if you can answer another question, i;ll be doing a tuneup (cleaning, replacing nozzle, strainer, etc) and it does Not have an oil filter, 2 line system, tank is in the basement, is it common not to have filter? system was put in 2000 thanks

[@grayfurnaceman]

+Dennis No-one I have never seen an operating oil furnace without a filter. GFM

[@dennisnoone7427]

i checked both lines from the top of a tank to a furnace and inside the furnace No oil filter, i just recently bought the property, is it amazing it's running since 2000? i want to see what a pump strainer will look like.

[@grayfurnaceman]

+Dennis No-one Pretty amazing. GFM

[@haywire1999]

hi, we have a wood furnace with Honeywell fan limiter switch and the fan runs constantly... even when fire is cold....we are thinking on replacing limiter switch ??

[@grayfurnaceman]

If you tap the control and it stops, you need a new control. Hope this helps GFM

[@haywire1999]

grayfurnaceman thanks, cheers !!

[@haywire1999]

grayfurnaceman what should we reset the limits to for wood furnace??

[@grayfurnaceman]

haywire1999 Most of these limits won't go above 200 degrees, and I would set it there. GFM

[@SilverlingVirtualStudio]

So if my off is set to 80 and the on is set to 100… is that why my fan won’t ever shut off?

[@grayfurnaceman]

Yes. Try off at 100F and on at 140F. GFM

[@holymolybullykennels900]

I had a bad fan limit with no auto/manual fan switch and replaced it with my buddy's that does (he just upgraded to a new furnace and pulled some parts of off his old) now I already checked to see if the bi metal rod was the same length and it was so I thought i could use it the problem is now that my old one was hooked up with 4 wires and his was 3....1 wire in top left, 1 wire to top right and 1 wrire bottom right. So i wired everything exactly as the old one and with the extra wire I had I figured I put it in the last open slot. But now the blower motor runs continuously and will not shut off even when the call for heat is satisfied. Please help. Thanks in advance

[@grayfurnaceman]

First, the manual switch should be pulled out during normal operation. Then it should run with the furnace. Is there a jumper in the switch? Should be a copper bar between the 2 lower terminals. If so, remove it. His furnace was set up with the fan switch and limit in the high voltage. Yours was set up with the fan in high voltage and the limit in low voltage, so the jumper must be removed. By the way, with it the way you have it, you probably have 120v at the thermostat! Hope this helps. GFM

[@CarlosRodriguez-wo1pp]

Hi, my sister has a furnace that is working more faster than before, as soon its started the flame come on, and after 2 minutes the fan come on too, but after 1 minute the flame go off and the fan stop after 1 minute, as soo its stopped the flame come on again, it have to be a problem with the fan limit?????, thank you for any help!!!!!!!!!!!!!!

[@grayfurnaceman]

I would look for plugged filter, plugged air conditioning coil, collapsed duct. another possibility is a thermostat problem. Hope this helps. GFM

[@AK-zt1mo]

Hello grayfurnaceman When the furnace wants to start the motor starts humming, as if it's not getting enough starting voltage. Could the limit switch be normally closed all the time and it's causing the motor to short Thanks

[@grayfurnaceman]

+Ashor K No. If the motor does not rotate easily, the bearings have failed. If the motor turns easily, the capacitor may have failed. Hope this helps. GFM

[@AK-zt1mo]

OK I tried to look for a capacitor and can't locate one at all (could it be internal). And I already tried a different new motor and it's doing the same thing. By the way the squirrel cage fan rotates smoothly, and the belt is at an ideal tension.

[@grayfurnaceman]

+Ashor K If it is a belt drive, it may not have a capacitor. About all I can think of is a power problem. The limit has no connection to the motor. Is the voltage correct? GFM

[@predigested]

My blower fan will not turn off and blows cool air once the furnace shuts down. If I flip the fan switch to manual, then back to auto the fan will shut off. Bad limit switch? my dial is set to 110, 160, 200. Thanks

[@grayfurnaceman]

Your fan switch is probably sticking on. Replace it. GFM

[@grassroot011]

Set it this way and there still is a lot of heat left in the exchanger, doesn't run long enough to let the humidifier do it's job. Set the off pointer lower and it short cycles.

[@grayfurnaceman]

That sounds backwards. Short cycling comes either when the pointers are too close together or the off setting is too high leaving enough heat left in the heat exchanger to heat the fan element enough to start it again. As for too short a cycle to let the humidifier do its job, there are several possibilities here. Oversized furnace, anticipator set for too short of cycles, thermostat location too close to diffuser. You can also try setting the fan on continuous. That will assist the humidifier somewhat depending on the type of humidifier. GFM

[@duramarks]

My blower motor is running constantly. I'm not sure why. If I unplug the blue wire which I beleive is motor speed 3 the ac works fine. With that blue wire unplugged the furnace will just short cycle

[@grayfurnaceman]

Mark what brand and model? GFM

[@duramarks]

grayfurnaceman It is a Heil 7000

[@duramarks]

Does that help?

[@deibertmichael]

If you have enough heat in the exchanger and it goes back on for a minute then off what can I do? Thanks!

[@grayfurnaceman]

michael d Separate the on and off tangs a little farther. GFM