Top 4 Reasons Why a Gas Furnace Short Cycles! HVACR Service Call Troubleshooting Tips!

[@acservicetechchannel]

The E-Book and Paperback at our Website: www.acservicetech.com/the-book The Paperback at Amazon: www.amazon.com/shop/acservicetech Support the Channel- www.patreon.com/acservicetech Tool List- www.amazon.com/shop/acservicetech For those that are looking for the tools used in the videos: (Linked Below) Related Videos: Thermal Limit Troubleshooting- kzbin.info/www/bejne/hHnSd39ur5qtfac Top 10 Pressure Switch Problems- kzbin.info/www/bejne/mIqZgpakoceoqquEressure Switch Troubleshooting- kzbin.info/www/bejne/rGq0iHyobrl8jLd3leaning the Condensate Tubing- kzbin.info/www/bejne/nabJZId7iMdmjJI Pressure Switch testing and Replacement- kzbin.info/www/bejne/bIGZo2mGhKx7esV8ow The Pressure Switch Works- kzbin.info/www/bejne/b3Wkdo2soN6Cb6M Why The Pressure Switch Wont Work While the Condensate Drain is Clogged- kzbin.info/www/bejne/jnykqq2knM2fqNGJsing The SDMN6 to Test Pressure Switches- kzbin.info/www/bejne/o3zXeH9ug69obrM ECM Blower Motor Testing: Make Your Own ECM Tester- kzbin.info/www/bejne/onzWepqgeq93f6s X-13 ECM Blower Motor Testing- kzbin.info/www/bejne/iZLQdqiJr9uMmKd5CM Variable Speed Blower Testing- kzbin.info/www/bejne/oqDGf6lvjNiUpKM 10 reasons Why The Blower Motor Won't Turn On- kzbin.info/www/bejne/imbNZYRuj9WSp80 4 Reasons Why the Blower Motor Won't Shut Off- kzbin.info/www/bejne/rYmWmXanrLqdoaeLhat Type Of Blower Motor Do I Have- kzbin.info/www/bejne/e3nahY18q9tgaLM 240 volt PSC Blower Motor Fan Speeds-kzbin.info/www/bejne/a3ishZqph9KGkJY How to Tell the Difference Between Blower Fan Motors- kzbin.info/www/bejne/e3nahY18q9tgaLM Gas Valve Troubleshooting- kzbin.info/www/bejne/m6a4o6ico5t0qat3ombination Gas Valve, How it Works- kzbin.info/www/bejne/bZ6Yi3eshNSJrbc Smart Valve Troubleshooting- kzbin.info/www/bejne/p5vVo4ujgdF_iMU 750mv Thermopile and 750mv Gas Valve- kzbin.info/www/bejne/qJrEf5KgatmgjpY Furnace Flame Sensor and Rectification Troubleshooting- kzbin.info/www/bejne/gqXJmJuLjsufY5Z8ow Flame Rectification Works- kzbin.info/www/bejne/oZe0Y5ysp5maidk Single Rod Spark Ignition and Flame Rectification- kzbin.info/www/bejne/fX-8lYJ_q7ysr80 Two Rod Spark Ignition and Flame Rectification- kzbin.info/www/bejne/moaplImAja9rjMk Troubleshooting the Furnace Control Board- kzbin.info/www/bejne/ppnWhoyupJxooLc Thermostat Wiring to a Furnace and AC Unit- kzbin.info/www/bejne/faC3mXSihNuGqtU Heat Pump Thermostat Wiring Explained- kzbin.info/www/bejne/qpeVgKt5edyffLs Thermostat Wiring Diagrams- kzbin.info/www/bejne/nmOXXqFvoN6qZtk Clogged 90% Furnace Heat Exchanger- kzbin.info/www/bejne/qX_PiI17r7iZqKM Why the Furnace Sequence of Operation is Important- kzbin.info/www/bejne/q3zWg6OPotyfpK8 Electrical Diagnosis Tools: UEI DL389 Multimeter amzn.to/2xAdaJf UEI DL479 Multimeter with temp sensor amzn.to/2jtsUbJ Magnet Jumpers- amzn.to/2PyKPQZ Alligator Jumpers- amzn.to/2PxqJXn Irwin Wire Stripper/Cutter/Crimper amzn.to/2dGTj2V Water Column Manometers FieldpieceSDMN6 Dual Manometer Pump - amzn.to/2jyK5Ka UEI Digital Dual Manometer - amzn.to/2CWC6BD Supco Universal Adjustable Pressure Switch -.01wc -10.0wc - amzn.to/2G1y0py 3/16" x 3/16" x 3/16" brass barbed tee - amzn.to/2INSRhQ 1/8" NPTF x 3/16" barb fitting for reading wc pressure - amzn.to/2G563Bq Combustion and CO Detectors: Testo CO detector amzn.to/33yqkqK Testo 310 Res Combustion Analyzer amzn.to/2NuYAO5 Testo 310 Res Combustion Analyzer with printer amzn.to/33vLl53 Testo 320 w printer amzn.to/33xZbUz Vacuum Tools: JB 6 CFM Vacuum Pump - amzn.to/2nqbvo8 CPS 4 CFM Vacuum Pump - amzn.to/2DxgPwY Appion Valve Core Removal Tool - amzn.to/2uYr8WL Appion Blue 3/8" to 1/4" Vacuum Hose - amzn.to/2uYlVyc Appion Red 3/8" to 1/4" Vacuum Hose - amzn.to/2uYg6Ro Yellow Jacket 1/4" by 1/4" 3’ hose - amzn.to/2umtcod Appion 1/4" by 1/4" and 3/8” hose - amzn.to/2Zyxzx9 Uniweld 1/4" by 1/4" 2’ hose - amzn.to/2GFov1Y CPS Vacuum Micron Gauge - amzn.to/2v1nM3O JB Vacuum Pump Oil - amzn.to/2mGrlXy Checking the Charge Tools: Yellow Jacket Refrigerant Gauge Set amzn.to/2aenwTq Refrigerant hoses with valves amzn.to/2aBumVI Compact Ball Valve for Refrigerant Hose amzn.to/2KUisW8 QuickDisconnect 90 for refrigerant hose amzn.to/2MMtVcg RectorSeal Bubble Gas Leak Detector amzn.to/2ckWACn Fieldpiece ST4 Dual Temp Meter amzn.to/2wc1ME3 Fieldpiece Bead K Type Temp Sensor amzn.to/2DBwKfs Fieldpiece Wet Bulb Temp Sensor amzn.to/2RRI7Tw Fieldpiece TC24 Temp Clamp amzn.to/2qHLyjZ Refrigerant Leak Detection Tool: Accutrak VPE Ultrasonic Leak Detector amzn.to/2nFYKVe Shop through Amazon! Your Purchases through Amazon provide a means for channels such as mine to earn advertising fees from all purchases after clicking through. Prices are the same as normal.

[@mikelilly7285]

I'm a 26 year gas company tech and I would absolutely recommend this guy. I don't even know where he's located but he knows his stuff. Sadly, this is very rare.

[@paulrozinski1488]

He’s in southern New Jersey. I love his videos too👍👍👍

[@markgrove2030]

SO true Mike. Many often think the upstairs thermostat is bad🤪😝. Last note re short-cycling? Repeat after me....FILTER FILTER FILTER ha ha. I used to practice over-the-phone triage when my techs were buried overnite. Can't TELL you how many owners didn't even know there was such a thing. Crazy but true.

[@mikelilly7285]

@markgrove I turned a single mother's gas on a couple months ago that had always had trouble paying. I started her furnace up and it short-cycled the entire time I was there. She showed me her usage was 50 mcf/month. She lived in a 1 story flat about 1000 square. Of course she'd called the landlord time and again and no one ever checked it out. I asked about the filter and she said the landlord told her she wasn't allowed to change it but again, never sent anyone to service it. I told her to tell the owner that the GASMAN was changing it for her and she wasn't involved. No more short-cycle, no more high bills. Some people don't deserve to own property.

[@markgrove2030]

@@mikelilly7285 Right on. Lady prbly had/has many other issues too due to this creep. Good for you Mike!

[@Alienspecies635]

It’s because no one wants to learn anymore. Instead of studying and watching videos like this on their free time they want to play video games and smoke weed. I’m a tech started with all HVAC stuff and now also doing hydroponics, combination boilers and everything else I love it

[@brucebromberek327]

Thanks for the video. I was dealing with a short cycle situation that was causing my furnace to not keep up. 68deg when the thermostat is set for 72. The local repair/sales place said it was a clogged AC evaporator coil. Your video allowed to confirm that the flow restriction was causing the high limit switch to trigger. Cleaning everything, still short cycle. Then one of the comments mentioned an extra radiator for high efficiency furnaces. I pulled the blower mower, and found a radiator BEFORE the heat box, it was CAKED with hair and crud. Little elbow grease later and I have a system working like new. Thanks.

[@vernroach3413]

Your best yet...Just got off one where the flame rod was carbon covered, It stayed fired afterward, but even after cleaning that, when the Digital T stat was satisfied it would come right back on...No heat anticipation...Replaced that, bingo...12 year old unit, never serviced...Your a great instructor bud and that's from a former instructor...Just word of mouth service for old folks or low income anymore...It's a shame the gougers are out there, but they are...Thanks for the videos you do...Keep learning guys...It makes you better...Watch this man.

[@randyproctor3923]

Great explanation; thank you for taking the time to help out a cold homeowner!

[@rupankansal]

Thank you so much for this video. I see the light at the end of the tunnel. We have been having this issue for almost 8 months. Have few different companies come and take a look at it. So far no one could diagnose the problem. Instead left me confused. So very disappointing. I am going to have my husband look at this video and see if we can fix it our self. Or if we have some one come to fix the issue we wont be fooled this time. These days its so hard to find some one honest and sincere to his work. My experience lately is people are more interested in doing the rush service and hand out a big bill collect money and go. Makes me very sad and disappointed with bitter taste. And makes it hard to trust anyone.

[@havocrus1]

Also Supply air dumping on tstat, simulating false "satisfied". When unit stops, no heat or cool on tstat, initiates another call. Great vid!

[@mrshawterry6]

Sir you're good, if a person learning would know about 70 or 75 percent what you know, the furnace would stay running , here in Chicago, it gets cold, mine went out when it was cold about two years ago, i bought another furnace installed it, but i did do the things you're saying and fixed the 1 where the part went bad, i put it back in hooked it up and it worked like it did before, i took it back out, and installed the 1 i bought again, i'm happy now sir, because when it gets cold again, and that's when they really break down, if it does it again, i'll go down stairs, install the working one, test the 1 that went bag, order the part, and get it working again, i get a kick out of listening,reading, to learn things, Sir you're a bad man in a good way, you know alot.

[@YTsux24-7]

Always carry some extra pressure switch tubing on tune-ups and service calls. The ends can often be loose or cracked from age. This will allow air infiltration causing the pressure switch to not close. Also carry a paper clip to poke debris from building up on the pressure switch tubing port at the ID motor. Excellent lesson as always Craig!

[@acservicetechchannel]

Fantastic tips! Its always nice to check a pressure switch tube and have it disintegrates in your hand, ha ha!

[@walterbrunswick]

@@acservicetechchannel automotive silicon paste works wonders at preserving integrity of rubber in high heat dry spots

[@captainwillard4891]

Carrier/ Bryant….if the secondary is cracked, the pressure switch will not close, if the tubing is cracked…the secondary is failed. The secondary on those are pure garbage.

[@paulrozinski1488]

You’ll probably replace more pressure switch tubing than actual pressure switches. Very often, techs are quick to blame the pressure switch when in reality it’s the lack of vacuum causing the pressure switch not to operate properly. Must admit, I was like that also but now a little wiser.👍👍👍

[@structuresspecialist9743]

Dirty air filter can also cause short cycling. Best HVAC videos on KZbin!

[@jiangbian76]

This is exactly what I came across when I was doing the PM on the unit heaters for my customers. Greatest video on this subject, thank you.

[@acservicetechchannel]

Thanks a lot J Brian!

[@faithtoro24]

Thanks because my furnace randomly blew out and yes it was the limit switch was open so that means it's broken. Thanks for showing.

[@utumven]

Great video. fixed my furnace from short cycling... I always thought it was a plugged intake or exhaust it only happens in jan or feb after a snow or ice Storm. I never considered it to be the other end. When i pulled the drain hose off the blower housing water came pouring out. My drain tube makes a loop in the blower chamber and then to the floor drain and it was totally plugged with gunk. Cleaned it out and all is good now. thank you, you guys are awesome....

[@-ultravic661]

Wow. This was the most comprehensive furnace video I've seen. Thanks for all the info.

[@lkw5699]

Great explanation. I wish all hvac techs were this knowledgeable!

[@acservicetechchannel]

Glad you enjoyed it!

[@junebugjoe5914]

You explanations are spot on. No hype, no bull. Thanks!

[@acservicetechchannel]

I appreciate that!

[@ChrisSullivan-s4b]

I strive to be like you. You are an amazing teacher. Thanks for all you do

[@miguelquiroz1550]

Craig. You will be a great teacher... ! Always a really good content..... keep up this videos...

[@acservicetechchannel]

Thanks Miguel! I am an HVACR teacher in southern NJ, glad to help!

[@deanmartin1966]

@@acservicetechchannel Hmmm..... You don't seem to have an accent? Lol

[@sportsman042002]

He is a great teacher very good at what he does learned a lot from him and I appreciate it.

[@chuck2498]

My experience is usually that it is a dirty flame sensor, clogged filter tripping the high limit, or a pressure switch issue (especially when it gets really cold). The first two are self explanatory, but the pressure switch has a few different reasons, but usually it is being blocked from either a PVC pipe or hard water in one of the orifices from the tubes from the pressure switch.

[@BastrdMcQueen]

Obstruction of the combustion air intake or exhaust will upset the system indeed, including ice or a nest; or like one customer found out at midnight last night steel wool shoved way up the pvc for winterization against pests was bad idea too. Diagnosed with monometer T / meter technique learned on this channel.

[@danstarnes2375]

Natural born instructor! Explains the trade so well!

[@acservicetechchannel]

Thank you very much Dan!!! I am glad things come across well to you!

[@jaimesanchez6933]

Great info! Thank you! Helping me big time to troubleshoot my first condensing high efficiency furnace.

[@christophernogas5032]

Love the videos Craig thank you, I had a water logged inducer motor in a Lennox condensing burner a few days ago, the installers got pvc shavings down the flu vent and clogged the strainers on the collector box

[@bryantylerservices]

Craig! ,Great explanation as always you are very detailed and explain things in a way of sequence of operation, to make things easier to grasp/ understand ! Wonderful assett to all in the hvac field. Thank you for all your time.,and effort making these videos! As always,i watch all your videos, Even as a veteran of 33 years in this field,mainly as commercial refrigeration,i still learn something new daily. Thank you sir! Bryan Tyler Refrigeration Helotes,Tx

[@acservicetechchannel]

I really appreciate your note Joseph!

[@Robnord1]

In my work with furnaces in manufactured homes, quite often a simple bi-metallic coil thermostat is used. These have a 'heat anticipator' which is specifically designed to govern length of heat cycle. Just last week I had a complaint of 4 years of short cycling. The anticipator was set for shortest cycle possible. 5 min fix. : )

[@acservicetechchannel]

Great tip Robnord1!

[@dbru2650]

Great comment, I was about to point this out when I came across your comment. This was more of a common short-cycle problem with the T-87 Honeywell-type stats, for example. For a precise setting of the anticipator, I always removed the front cover of the stat and remove the white wire from the W connection then wrap a piece of single-strand stat wire 10 times around my clamp-on amp probe, then used the wire to jump from R to W on the stat to send the signal to the furnace. This would magnify the reading by 10 then remove the jumper and reattach the W wire. Then divide the number by 10 and set the anticipator with the exact setting. With the advent of newer electronic type stats, the anticipator problem has been solved by an integral amp reading and automatic adjustment. The anticipator was frequently overlooked by the installers but was often a nuisance call.

[@learnjcbskidsterchickensga7594]

We had six years of short cycling…air filter had no dirt around edges. Hvac new graduate found the installer did not follow air flow opening specifications, 1940’s farmhouse. 3 previous hvac maintainers did not catch this flaw.

[@ThePapa41]

Very thorough discussion, excellent list of associated tools and instruments. A clogged air filter will change the delta in the heat exchanger producing a high limit trip also. Louis

[@acservicetechchannel]

Absolutely correct, thanks Louis!

[@davidscottkrause1]

My furnace would start up and the flame would come on, but most of the time it would shut down before the blower came on. I thought it was a bad primary limit. But I noticed the high voltage line going to the igniter was touching several other wires (including the flame sensor wire), so I re-routed the high voltage line to isolate it, and haven't had a problem since.

[@thaison773]

Thank you very much for making this very educational video, I would like to add that a dirty A coil could be the reason for number 6.

[@patcassidy5997]

Great video Craig. Also, check the blower run capacitor. A weak capacitor can slow the blower which can cause furnace to go out on High Limit.

[@brianmcdermott2430]

Great video and info. Great guest too. Thank you Bryan and Craig.

[@emoneyblue]

Thanks for sharing. Do you have a video on why A/C unit cycles on and off really fast at the condenser?

[@sman5877]

I had the soldier problem on the back of the board on my Gibson . i think it’s called a cold soldier joint. it was not heated hot enough on the pin when manufactured. It was a easy fix . Thanks for such a detailed video.

[@blackishpariah]

I see this so often in the field

[@louisgholland709]

Goodman furnace stop working was running fine other day. The Mother board was changed last winter the blower was leaking water but was resealed water pump works fine. I turned thermostat control off main switch off to furnace Wait 5mn turn switch back on then control to 65° heat kicked on but fan not run then unit shut down.

[@quinsattorney]

Thank you. Valuable info for a home owner to save some bucks!

[@user-ql2bz8on7m]

This guy is 👍 👌 👍 👌 👍 👌 👍 👌

[@dougross4489]

You Sir are a natural teacher! Subscribed

[@acservicetechchannel]

Wow, thanks!

[@Stankuzak]

I was getting an attempt for the gas furnace to start and then quit going into lockout. I cleaned the flame sensor and reinstalled it with no difference. Meter is series with the flame sensor provided zero dc reading. Replaced the electronic board and the furnace is working great. The board is one of the top 5 things to go. It was on a Carrier Gas Furnace. So if you are getting no DC voltage back when the meter is in series with the flame sensor and the flame sensor has 110 volts, it is probably a bad board as it was in my case.

[@rocker8692]

I appreciate your videos,you make it easy to understand.I went to an HVAC school but I forgot to pay attention lol

[@acservicetechchannel]

Thank you! Grateful for your support

[@docfaceful]

I relocated my combustion area intake pipe,that was taking in (saturated with water) air( while it rains all the time here for a few weeks. The pipe was probably sucking in lots of raindrops into the combustion area.and as soon as I relocated that intake to combustion area pipe to a dryer area,it then stopped the short cycling

[@markcavelli9087]

100% appreciation of what you do.

[@acservicetechchannel]

Thank you for your support

[@andysullivan7226]

Had a couple of them disks switches that were weak. They still worked but would trip at different temps at random times.

[@acservicetechchannel]

Yeah absolutely, thats what happens! They rarely break completely unless it is at the contacts where they are burnt, thanks!

[@billl3936]

Ask the customer if anybody has done any electrical work on the furnace or if the power had been disconnected and reconnected. If you have the polarity backwards, the furnace will come on for about five or 10 seconds, and then shut the gas off. I know this happens with Rheem furnace not sure about some of the other brands.

[@fernandofrancisco3106]

Craig Happy new year to you and your family. Thanks for sharing your knowledge to everyone. God bless you.

[@acservicetechchannel]

Happy new year!

[@bruce8572]

I had this problem with the 80+ downflow gas furnace in my garage. I found that the thermostat was being influenced by the hot air from the furnace. I could have moved the t-stat, but I built a semi-shroud around it, so the airflow was minimal around the t-stat. Simple problem solved.

[@bladerunner1458]

Thanks UR a great teacher. I always adjust my equipment to run long cycles to make all the controls last longer. Unfortunately some of the new equipment it’s hard to adjust it to do this. I have a Bryant Hi tech thermostat and I can’t figure out how I can like send the heating cycle.

[@JosephFlynn-n1i]

I have a Lennox gas furnace & just did cleaning of heater have a problem with spark ignition problem. The furnace cycle of operation goes well, however spark ignition goes back on after heater is working.

[@OneManParade]

I just came across a short cycle furnace. It didn't give me a code but would fire up, run awhile then shut off. The grill cover was blocking the exhaust/intake

[@carlpasquali7965]

That was really good. If a new replacement, it could be too large.

[@gadgethunter5732]

I had a tricky call with an Armstrong furnace and short cycling . The fault code indicated the pressure switch was closed when the inducer was OFF. Typically the contacts have stuck together and a new pressure switch is in order. On this call the furnace wasn't that old, so I confirmed everything seemed normal. Plenty of static pressure to close the switches etc. A few days later I was back. Same fault code. This time, instead of using a jumper wire to make a call for heat I let the thermostat do its job. The tstat was short cycling the inducer . It has lost it's marbles and wasn't giving the fan wheel enough time to stop spinning before making another call for heat. Thus creating the fault of pressure switch closed with inducer motor off. I suppose if I were a way smart Allied Air engineer I would add some appropriate time delay logic to the board to avoid the issue. After installing new tsat , problem solved.

[@cbenson23]

Is it possible a faulty thermostat could cause a furnace to short cycle or cause it to shut down before reaching temp and then restart because it is not at temp?

[@douglasbottjer6942]

Just fixed my furnace because you're video. I checked the presure switch and the tube was cracked causing the unit to shut off.

[@Robnord1]

The most common cause of short cycling I see is a thermostat being bombarded by hot air from a poorly located heat duct. The thermostat being mounted too high on the wall can also cause short cycling.

[@acservicetechchannel]

Another great tip, thanks!

[@paulpeter2869]

Hi Craig! I wondering why you didnt mention a clogged primary or secondary heat exchanger for this issue. Is that not a possibility for this type of problem? Thanks!

[@vishansubasinghe140]

Hi Craig, this is a wonderful learning video. Learned a lot. Appreciate it! I just had my furnace do the cyclic shut off and immediate restart and immediate shut off... I remembered my wife brought home one of the high/dense furnace filter, which I reluctantly put in lately. I guessed that may be the cause and immediately replaced it with a very light/porous furnace filter, and the furnace just ran for 25 minutes without cycling... Hopefully that's it! Update: This id day after: Furnace cycles still, but not as frequent as before… I also have a tripping flame rollout switch, which only trips once in few days/weeks, so it may be or may be not related… I would check the thermal limit switch now….

[@cruzo9541]

you should not be manually resetting your flame rollout switch without actually understanding why it is tripping.

[@jamanewman3157]

Our furnace short cycles it runs a total of four times before it stops for a while I have the Merv 13 filter in my furnace and in the air return in the house so I'm thinking that maybe our issue.. I'm not sure.. so I'm going to buy a less dense filter for the furnace and cold air return in the house and see if that helps!

[@russellcrea9701]

What is the likely problem if my furnace short cycles and does not come up to temperature with a new clean filter in it, but when the filter is removed the furnace works OK? It worked in previous years with a filter. Thanks for any ideas.

[@learnjcbskidsterchickensga7594]

The thermostat? Yesterday we got furnace running York Stellar plus 1990 (2022 today) Replaced: blower inducer motor Flame sensor Will do ignitor but need tools to remove rusted screw Limit switch Thermostat…to simple old fashioned round type Honeywell Worked fine. This morning it short cycled every 15 minutes three times. Instead of 63 (20 outside feels like 12 degrees google says) I set it to 70 and it ran at least 30 minutes.

[@eddymumford4086]

I'm running my Goodman 80 percent gas furnace with the top door off... if I put it back on it will thour code 3 an it will start right back up it seems good for now it don't come right back on anymore. I think I have to clean the burners I did see a spider web very little one...

[@jc_yadigg]

how do you increase the blower motor speed? i have a brand new unit that will run for about ten minutes on the first run after being off a while and then run for about 30 to 60 seconds there after indefintely until it sits for long enought without running.

[@tirregrelleumekuk3635]

gas flow can cause gas pressure sensor problems. If there is restriction via faulty regulator or dirt in line then gas pressure can read fine until furnace starts and flow restriction can't keep up with demand. This results in low pressure at safety switch shutting it down/ short cycling.

[@CC-io3nc]

My boiler burner runs constant when the flow temp is set at 70c. However when in lower the flow temp to 60c it constantly cycles on and off. It'll start when it drops to 50c. Starts back up for about 10 secs till it hits 60c then the burner will turn off again.. I assume this is actually more inefficient? As the constant stop start will cause more wear and tear in the boiler?

[@xredman002]

rheem gas furnace gets voltage, fan starts, pressure switch engages, gas turns on, flames ignite, heats up for about a minute and a half. Then when its time for the blower motor to turn on it just clicks and goes into error. the board is getting voltage and the capacitor has been replaced. Does this mean that the board is bad?

[@LarryDuguay]

Anything that prevents the right amount of airflow across the heat exchanger can cause an excessive temperature rise such as: a dirty filter, a loose blower belt, a filter with a high MERV rating, or a restriction in the ductwork. Other causes could be a return temperature too high from an improperly designed duct system or in the case of a zoned system, a n improperly functioning bypass. Lots of things can go wrong and it may take some detective work finding the cause. I once had a new install where the pvc vent was constructed of schedule 80 pipe and that was enough restriction for the pressure switch to shut down the burner.

[@narinderkaur344]

Hi Craig, I need to switch off my furnace and wait for minimum thirty seconds and then switch on again and furnace start working again normal ( Ignitor comes on and valve throws gas and then there is flame). It works ok for minutes and if needed hours but once cycled, Inducer motor keep running all the time but flame don’t come back. Please help me on this.

[@andresbarragan8595]

Guauuuuu good job im from Chicago I vn watching some of your videos thank you so much

[@blackishpariah]

Great video as always

[@acservicetechchannel]

Thanks a lot Kenneth!

[@SeanBaker]

My issue, a year or so ago, was my thermal limit switch was tripping too soon. Had the HVAC company replace it, and all was fine. They needed to lower the gas pressure a bit also.

[@acservicetechchannel]

Yeah sometimes they just wear out over time, thanks!

[@macbagpipethehaggis3213]

Hope they did a combustion analysis

[@bobsoft]

My furnace was short cycling due to a faulty smart valve (Honeywell) The capacitors inside it were failing due to age (high ESR) and were causing the voltages to cycling up and down. This made it impossible to hold open the solenoids for gas flow.

[@acservicetechchannel]

Nice, thanks for sharing!

[@waterfuel]

My Powermate 3400W generator won't turn on my NEW gas furnace! It did run the old oil furnace. When utility power to house came back on, the furnace started. The generator sockets have 3rd ground hole The ground is already connected to neutral side. The power out at end of 3 prong extension cord was 60cycle AC 117volts. The cord was checked for ground at both ends. What's wrong? The male plug on furnace side has poor ground. The socket on furnace has loose connection for plug. Is the new gas furnace in lockout mode? Service sheet says no power. No red light on board. Door switch has power. Does the new Airtemp gas furnace have a timed off period before allowing main circuit board to turn on? No response from contractor. He has the plague......

[@Rbhsr4u]

Please talk about duckwork is sizing too small it makes systems short cycle by Opening the high limit switch for the heat exchange Thanks! Greg for your videos you're awesome dude

[@williampaul8979]

Hello Craig, first off I really appreciate the awesome video. Secondly, I am going to be installing my first heat pump air handler in a few days as a part of an interview. I have been looking all over the internet for a video of how to wire the high voltage (not low voltage thermostat wiring If you accidentally misread it) from start to finish. I would greatly appreciate if you could. You are the only tech I feel would make a great video on how to do so. Also are there any other tips you would give someone installing a heat pump for the first time. Just FYI I have been doing hvac for a little while now. I have wired condensing units, indoor furnaces just never a heat pump air handler.

[@acservicetechchannel]

I don't have a video on exactly that but you need to have a disconnect switch within a servicable distance from the air handler. Often we put it on or right next to the air handler. Make sure the wire is cased if it is indoors such as in MC, seal tight, metal conduit. Check to see what kw heat package is installed and if it has breakers or fuses attached as the incoming power wire to the air handler. If it does then you know what amperage the wire must be and what breaker size in the breaker box the wire should be protected by. If it is 240v whip at 30amp then 10 gauge wire, 40amp then 8 gauge wire, 60amp 6 or 4 gauge wire, 90amp 2 gauge wire. Of course whips can be a slighlty smaller size since they are a short distance but I usually still size them the same as I would a long wire run so it is not a weak link. Anyway, if it does not have strip heating then it may just need a 15amp breaker which the air handler can be wire with 14 gauge. However if the breaker size in the building is 20 amp then 12 gauge wire would be used. You need to look at the rating plate of the air handler though to verify what it says as the max amp rating to be sure of the size if there is no strip heating. If aluminum wire is used then anti oxidant compound must be applied to the stranded alum connection before tightening the lug. Make sure you are not doing more than just working in the disconnect, whip, and tying unit in unless you are a licensed electrician. I hope this helps you!

[@williampaul8979]

Thank you. I hope I can be as good of a tech as you some day

[@TravisHaug]

My furnace is acting inconsistent, and at times it will short cycle, and other times it will run fully. For instance, while servicing the unit, it got down to 64 degrees, it then would heat to 68(we have it set to 69) and then continuously short cycle and never reach 69. I pulled the flame sensor and cleaned that off and the inside of the case, but it seems to still be doing it. I swapped out the filter for a higher flow filter. My next step I guess is to possibly replace the thermal limit switches. Also bought a Nest to replace my ecobee as the Ecobee would call for heat and the furnace simply wouldn't turn on. Replacing that momentarily, as well. Anything I'm missing?

[@markc1310]

I have a Goodman furnace from 2006. It runs for 7-8 minutes sometimes longer then shuts off, blowing warm air still. Then turns back on for 7-8 minutes. And repeats itself. I’ve tried cleaning the flame sensor and metal by the sensor. Checked the pressure switch lines, and switch seems fine. I ordered one but it hasn’t shown up yet. I cannot figure it out. I’ve cleaned and checked all connections. I don’t get an error light blinking. It’s just either solid or goes off. I believe ventilation is fine. I’m wondering if it’s the thermal sensor. But I’m not sure where to find it. It still keeps my house warm. But it can’t be good for it. I hate calling somebody out because it’s a few hundred dollars just to have someone show up. And I work with electronics.

[@michaelsmith4784]

Is it ok to jump the wires from my faulty upper limit switch for a week or so until my new switch arrives?

[@johnthomson8332]

My sequence works until the blower fan kicks on and immediately shuts the furnace down after about 1 minute of blue flame. It flashes a 42 code witch says check the inducer motor, it seems fine, no weird noises. I cleaned everything and tapped on the inducer motor with a screw driver and the furnace started working again for about 2 hours. It started doing the same thing again. Any thoughts.

[@bob56063]

Should the flame rectification be erratic like jumping around between .01 to anywhere up to 2.5 but spends most of the time somewhere around 1.0 to 1.5 but jumping around? The flame sensor looks like new but I did go ahead and cleaned it and checked for cracks in the porcelain and didn't see any. Any help would really be appreciated . Thank You Bob

[@RegniA]

Great video! I still have a problem with Amana furnace. After I set the thermostat at 69F the furnace was on at 67F and off at 71F; but didn’t start again when for another cycle. The red LED light on the control board was on indicating normal operation. I turned off the power to the board and back on after 30 sec and the furnace turned on. After the cycle ended, the furnace would not turn on again unless I turned off the power to the control board and back on after 30 sec and the furnace turned on. After the cycle is over, if I try to turn on the fan only, it doesn’t start. Do you have any suggestions?

[@skiz888]

My furnace was short cycling at the end of last winter. I called an hvac guy who ran some tests and said it was a bad DATS, so he bypassed it and said that should fix it. 15 min later it short cycled again. He came back and troubleshooted again and said it was something else but I can’t remember what he said it was. He didn’t have the part and left without fixing or coming back. I wonder if it was the thermal limit? I now likely need to have another plumber re troubleshoot for me smh. I can fix it myself if I know what part it was, but I texted him and he can’t remember because his paperwork just references the DATS because that’s what he thought it was when he left my house before having to come back smh. Any thoughts?

[@TH3GR33NG33K]

Wow super knowledgeable! Thanks for the info! Cheers!

[@acservicetechchannel]

Glad it was helpful!

[@anthonytortorice1264]

Craig thank you, yet another awesome video. Happy holidays my friend. I know this isn’t a Q&A type of forum, but my question ties into this video. I have a problem with my gas furnace cycling, but only when it’s overly windy outside. I was wondering if anyone else has experience this issue. I really do nothing in the way troubleshooting. Just play with the system a bit and it fire back up eventually. Sorry for long post. This is just annoying me as the temp is dropping here in NJ.

[@davidscottkrause1]

I had this problem when it was very windy outside (50-60 MPH gusts), it was sometimes causing a down-draft that would shut off the furnace flame, then a second later the flame would come back on.

[@mike6636]

I have Goodman gmec961005cn 2stage furnace. When its fire shuts off, its blower motor shuts off right away. Manual says it suppose to stay on for 150 seconds. How to set up so blower motor still stays on for at least couple min after fire shuts off. It reach at desired temperature too before fire shut off.

[@chrisguillen1495]

Doesn’t the board first check to make sure the pressure switches are open? Then the inducer draft proves them closed?

[@johntimlin6664]

I had a (carrier) 80+ would go thru sequence but cut out as soon as it would ignite roughly 1.5 sec. Check all safeties , flame rod , press switches eventually found out it was the board as soon as flame engaged it shut down the unit. Replaced pc board

[@denisfedotov3200]

My Goodman furnace would go through a full cycle but the flame would not ignite. After 3 attempts it would shut down for a longer time and then try again. I cleaned the sensors. It did not help. Then I took the front panel off and the furnace worked after the first attempt and was working normally. It seems like with the closed front panel there is not enough O2 in the air to make the gas burn. I snaked the pvc pipe that supply the air from the street (it is a high efficiency furnace). The supply air pipe is free. I wonder if the induction motor may be getting weak to suck enough air from the outside for proper combustion? Right now I got the front panel open about an inch and the furnace works fine. As soon as i bolt it down the problems start. THank you

[@amanpreetsingh3863]

I have same issue ..have you figured out something ???

[@williamtwiss1664]

Just replaced my furnace with the same type furnace same make & model , Hamilton Winchester furnace . My thermostat worked fine with my old furnace (i replaced because it was 18 yrs old ) but now with my new furnace , same thermostat hook up . It will start up & run fine , but i had to turn it up to 90 to get it to shut off about 70 . Then it would not restart un less i returned it all the way back to zero , then move it back to a normal position before it would come on . This furnace seems to get hotter than my old furnace. I even put on a replacement thermostat , but no good same function . Could it be i need a newer style hook up with a newer style maybe digital thermostat

[@drewn4344]

I have a heat pump, and the interior blower motor began blowing air very slowly. It's not on slow speed, the blower is barely turning. I checked the relay and it's okay. I Haven't took the blower motor apart yet. I wonder if a hard start or auxiliary capacitor might be needed. I have a rheem RQRM-A036JK010 model.

[@chuckquinn8026]

Excellent video!

[@acservicetechchannel]

Thanks a lot Chuck!

[@jeffhelman1721]

My unit is 4.5 ton Goodman gaspac it's sticking in the cool down phase and I have to cut the power at breaker box and restart to get it working again I also noticed that it goes through a couple of false starts before it gets running and the air is not really hot like it used to anyone out there have any suggestions?

[@dennisqwertyuiop]

great teacher

[@acservicetechchannel]

Thanks a lot Dennis!

[@waltradcliffe4482]

People that won’t do needed maintenance can have this problem too clogged filters clogged fan and coils cause low air flow and higher temps

[@acservicetechchannel]

Absolutely correct! Thanks Walt!

[@andysullivan7226]

We have a service call where a unit trip out the high limit switch. Alot of troubleshooting and the only thing we found was the hot air was being pulled into the return (return and supplies in ceiling and this is an old church we didn't do this ductwork and had to reconfigure, didnt like it from the start.) Thermostat was right by the return about 2 foot below. The hot air was not reaching the thermostat to satisfy, cause the furnace high limit to trip. The whole setup was screwed, we moved the return down below thermostat and relocated the thermostat. Problem solved. We didnt have many options for relocating anything else, they just had a company install this system. Crappie install caused this one

[@cdarrell1985]

If the filter and fan are dirty, there is also a good chance that the secondary heat exchanger fins are partially plugged also depending on the style of secondary used.

[@averagejoe3312]

Wild question ya. My furnace kicks in and heats just fine, but my cool down kicks in to soon and it won't kick off until the house is freezing. When I turn down the thermostat a degree, it will do just fine. I use to keep it on 72 a couple of years ago, but now I am down to 69 degrees. Why do you suppose it is doing that? Just as a guess.

[@cliffBMRC]

Excellent instructional video. Thank you.

[@acservicetechchannel]

Glad it was helpful!

[@kenliu1105]

Excellent video! I have a question. I have a short cycling issue with my tempstar furnace. I checked the collector box and found that the corners and edges inside the collector box were melted. What type of short cycling can cause that melting.

[@cfsmound3524]

Hi can you tell me what the dip switches should be at on a new carrier 59TP6 100k BTU furnace I have a ecobee and my installer just left it at the factory positions and told me to leave fan on all the time.Thank you

[@brianjohnsen5970]

Gas valve is shutting down the burner when the blower is fixing to start, checked the thermostat switch it’s closed, don’t understand why its shutting off the burner when it’s about blow warm air into the house.

[@renteria4540]

Really good information thank you very very much . I appreciate it

[@calderart]

Wow. Extensive coverage. Mine is short cycling but there is no error code. We've done so much troubleshooting to no avail. The thermostat temperature is equal and the furnace fires up still. It's propane Intertherm, model MG2S - 045F2ABM1 in a single wide manufactured home.

[@-ultravic661]

My short-cycling furnace didn't show me an LED error code when i turned off the thermostat and went up to my attic to investigate. Note: My cycling only occurs during extra cold weather (under 50 degrees F.). I then had Wife turn on the thermostat as i sat in front of my furnace and watched it run. It fired-up and ran a bit, then failed. This time I saw the #33 code (3 short dashes & 3 long) before it disappeared. . Now I gotta fix it.

[@calderart]

I have since found out that the short cycling was due to faulty electricity/hydro. The main supply to the Aloha Manufactured Home and RV park was shorting out so the power was always fluctuating. The park being a 60AMP service didn't help. (It still is.)The 'switch' finally melted and had to be replaced at $20G+. It turns out it could have been avoided if regular maintenance was performed. It's been faulting for years and increased in the last 10 months I moved in.

[@zorst99]

This is my problem do you think this would be the switch .......Problem: When desired house temperature is reached the heating portion of the cycle terminates, but the furnace blower fan fails to turn off after removing excess heat from the furnace. The furnace must be manually unplugged to accomplish.

[@pilotguy13]

Well. 4th reason is water not draining out of the factory setup water separating system. I keep having to pop the drain tubes off and blowing out the white box on my Goodman

[@sandymilne224]

I seem to have a condensation problem in the cold weather. The furnace ends up blowing cold air. I just don’t understand how the clear plastic ‘housing’ functions. I pull off a hose lower right of the housing and lots of water comes out. Sometimes that clears the issue, but I don’t also understand why the drain hose on the lower left never has any water in it. I was told that too much water in the housing kicks out a sensor, so to drain the housing. Really??

[@nicetna2010]

As an industrial engineer, I'm of the opinion today's gas furnace is over-engineered and constructed with faulty/inferior designs and materials. Simple solution: heat with wood. More BTU's for less money, along with basically no maintenance other than the annual chimney sweep. Of course, not all applications will allow for wood heat.