HVAC Furnace Short Cycling - How High Limit Switch Works

HVAC furnace short cycling and not staying on long enough.. There are a couple reasons why a gas or electric furnace can be short cycling. One of the most common reasons is that the high limit switch is tripping and that is what is causing the furnace to short cycle and struggle to get to the temperature set on the thermostat. In this video I explain what the high limit switch is, how it works, then I test it and do some experiements with a few switches, and lastly take them apart and see what is inside. It's an educational ride, enjoy!
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#furnace #furnaceshortcycling #wordofadvicetv #furnacenotheating

[@politicsreporter4247]

Thank you very much Friend, Today one of your Videos saved me $$$ and my family from a freezing night. There was a minor issue with my Furnace that I was able to fix. I am not a professional in this field but your videos must be great help for pros as well.

[@PMartian]

A L O H A! This video came at the right time. Along with your other videos that explain the High Limit Switch has helped me to diagnose this as my possible issue of the burner coming on then off and then on again after a few minutes of the furnace running. The control board also showed the 4 LED Flash Error. Again your videos are helpful for us DIY and money saving "can do it myself" community. You helped me diagnose and self replace a blower motor and fan a couple summers ago with such great direct communication which I am still so thankful for. Saved me over $1200.00. Enjoy island life!

[@PMartian]

How likely is this switch to go bad on a 21 year old furnace? I am hearing it's rare but possible.

[@borys444]

Can’t forget how u helped to get my furnace working again a few months back. U da man peace brother!! Thank u for all that u do Like button-SMASHED!!

[@WordofAdviceTV]

Love to hear that!! Glad you were able to fix the furnace, stay warm! Smashing the like button is always appreciated, thank you!

[@HD-pc4id]

Literally just had this issue with a Bryant from 300 years ago Just want to say that your videos are awesome

[@WordofAdviceTV]

Haha a 300 year old Bryant sounds pretty old 😅 Thank you! Glad you enjoy the videos! 🤙 I appreciate you stopping by and leaving a comment 🙏

[@markb9420]

This is a comment on the dl389 meter that you recommend from a previous video. I bot one and love it so far. But I have a comment and a caution on it. First I was surprised that I meter of that quality doesn’t have a fuse in it... I have a couple cheap ones and even they have one in it. Second, be careful when measuring voltage because according to the manual the common lead should not be exposed to more than 25 volts.....so be careful that you put that lead on the neutral or ground. THANKS for all your videos and education! :)

[@SuperComfee]

Hey I'm a Gas Technician out in Ontario, Canada. I'm a huge fan of your video's, thankyou so much for helping me understand HVAC better. Keep doing what you do man, love it.

[@sihyungpark8311]

You're truly the everyday hero!

[@WordofAdviceTV]

Lol, thank you!

[@fefkimuslija4188]

I am a retired HVAC tech, and I do like your videos.. You do know how to explain things very clear and simple. I know everything that you tech,, but I still like to watch you.

[@terryrobinson3624]

Do it matter which contacts you hook your meter to

[@bryang7035]

@@terryrobinson3624 not when testing continuity.

[@hvacservicementor]

Great explanation! Remember that limits and rollouts are safety devices that prevent catastrophic failure and fire! Never jump out a limit!

[@WordofAdviceTV]

Thank you for the safety reminder! Much appreciated!

[@PTN164]

Thank you for sharing a good video for those who are interested in HVAC. God bless you and your family members all.

[@WordofAdviceTV]

Thank you! May God bless you and your family as well!

[@michaelcostello6991]

Great demo of disc popping up on table and flying off

[@WeisM3]

This was the problem with my furnace. Thank you very much!

[@donc.8019]

I like your videos .. This is exactly what I wanted to know ! Will follow

[@VanNguyen-ij7sh]

Very educational.....extremely entertaining....thank you Jay!

[@WordofAdviceTV]

Glad you liked it Van! Thanks for stopping by, aloha from Hawaii!

[@jimbola77]

love all your videos!!!! thanks a million for sharing!!!!.

[@2kdhrubo]

You explained very well sir, i love your hvac video

[@bamboosmith4294]

Fantastic demonstration great job keep it up and keep on rolling nice

[@Crappie_Hunter_Seeker]

Great job as usual !

[@Kids_Very_Fun]

You are good I learn lots from your video thanks you so much for what you doing .

[@harrychang9376]

the best of the good technicians.

[@leedskalnin4571]

Hi hay you are the best I like your videos. Everytime I each one of your videos I learn a lot. Keep up the good work.

[@WordofAdviceTV]

Awesome! Good to hear that the videos have been useful. Thank you for the positive comment, have a great weekend!!

[@creekmud2857]

Just to be clear though again I quite enjoy your videos and I love your showmanship! I cannot perform on camera near as well as you do.... And I really love your performances whether you call it right or wrong I still love the performance! in fact I don't see why your channel has not exploded you do perform so well while on camera!

[@WordofAdviceTV]

Thank you Arin! I am happy to hear you are enjoying the videos! I think with some practice you would be able to make videos like this or even better too 👍 Keep in mind that I've made hundreds of them so far. It may not be obviously noticeable but there are actually a lot of editing cuts in this video. Just like most other content creators I have to stop and retake many times. For example, this 18 minute video actually took over an hour to film. The guys that are truly good are the ones that can make a video like this without having to do any cuts. Now those guys are the real talent out there..

[@creekmud2857]

Just a question. Have you ever told a customer that their flux capacitor was bad? Every time I have a customer between the age of 4o and 50 years old and they have a bad capacitor I tell them I had to replace your flux capacitor! But the slightly younger and slightly older ones say they've never heard of that lol.... In 40 to 50 year olds always say that sounds very familiar! I instruct them to go to O'Reilly Auto parts website look for part number 121g.... If you haven't done this I strongly urge you to!

[@WordofAdviceTV]

@@creekmud2857 Haha that sounds fun! The capacitor from the future! Or is it from the past? I'll have to try that sometime 😄 I was not aware that O'Reilly actually has a page for the flux capacitor! That is awesome!! My respect for O'Reilly has gone up 😎 Thank you for sharing!

[@adeadchipmunk7713]

love ur videos very entertaining and interesting

[@Jack.333]

Thanks Again Jay. Great addition

[@WordofAdviceTV]

Good to have you John! Thank you!

[@nickmakowski3240]

Ur a life saver great video!

[@jiankang813]

Thanks for the very helpful and educational video. I have watched your videos a lot. One question I have: for those non-automatic reset temperature limit switches, I can easily determine which one is off with multimeter after a shot cycling run. However, for those switches with automatic reset, they might already get auto-reset before I could measure them. So is there a easy way to detect definitely it is an auto-reset switch problem ? Thanks

[@nilbertocohen4963]

Excellent Video.

[@lukehodgson5222]

I'll bet your not missing the polar vortex in the midwest right now! Thx for the vid.

[@whitingservicesheatinganda3858]

Great video!

[@taiebjerbi5419]

Thank you, you are amazing. It is interesting, Keep doing things like that.

[@WordofAdviceTV]

I appreciate the comment! Thank you and I do hope to make more videos like this one 👍

[@GotchaplumberGotchahvac]

Another good video!

[@pablolopez973]

Thank you for sharing your videos.are very helpful

[@WordofAdviceTV]

Glad to hear the videos are helpful! Thanks for stopping by, have a great weekend!

[@jolyperson2]

Jay, no doubt you’re a great teacher. Would you please make a detailed video on sub cool and superheat for beginners. Like when to use superheat and when to use sub cool method. Also if you can show how to use and read PT chart. I’ll really appreciate that. Thanks a bunch and have a great day.

[@WordofAdviceTV]

If I get the chance, I will try to make a video like that. Thank you for the suggestion! Have a great weekend as well!

[@jolyperson2]

@@WordofAdviceTV thank you

[@TheRiverRats100]

Great videos

[@diegodelmar1190]

hi jay its Diego Again and want to thank you for your informative video clips! Indeed you have a teaching gift and how I wish you were my instructor at Trade School. Ive learned more from your videos that the 6 months Ive been in trade school! Anyhow maybe its because the instructors are overwhelmed with the large class/students. Regardless please, please keep the videos coming and as you are my encyclopedia for HVAC! By the way Jay Im thinking on buying the SMAN 480 Digital Fieldpiece gauges that offer an slew of readings all in one package as opposed to the Yellow jacket analogue gauges which take more time and effort in the field diagnosing problems. Any advice my friend. Maybe a Video? Thanks Jay!

[@KendallRoberg]

Aloha Brother. Watching this from the Big Island. Mahalo

[@jerrysarabia8930]

Thxs dude great insight

[@Ash-cy7yw]

Thank you SO much for what you do. Really helped me. One question if I may. I have the style of switch like the first one in your video. I notice you show the flame example with the 'button' pointing down. Is that how it is also supposed to be installed? Pointed down towards the burners? If I do that then my label in the outside is upside down. Is that okay or does the label need to show right side up which would have the sensor 'button' facing upward and the flame would be hitting the bottom of it. Thank you in advance if you are able to answer my question!

[@JuanSanchez-nn1db]

Perfect. Thanks

[@7minnow]

GREAT JOB your the best

[@creekmud2857]

Buddy that right there has never been called a flame rollout switch or a fan limit switch! That is called a main limit switch. A rollout switch is down by the manifold area in the beginning of the heat exchangers! It's job is to sense extremely high temperatures and prevent fire or explosion! A fan limit switch is to detect heat coming back towards the fan indicating that the fan is not running at all! And that switch right there in your hand my friend is designed to prevent premature failure inside the machine due to poor air movement! I don't mean to come off as a smart-ass but I have a whole lot of customers that watch videos like this and then they get really upset when I show them the actual definitions to these parts! You can feel free to send me a message if you're not sure what a part is called or just Google it! Either way I get a kick out of watching your videos that's why I subscribe to you.....

[@WordofAdviceTV]

Thank you Arin! I do appreciate you spelling out the specific definitions and purposes of the limits that I showed. I should have done a better job of explaining that they have different purposes. I was too focused on how the thing works. Buy anyway, thanks for this comment! Now this info will at least be in the comments section.

[@ysosirius2886]

good job

[@aidenstone5632]

You really should do a video on heat pump wiring and how to troubleshoot them

[@nickaryan100]

you are so ggod in explaining, thanks

[@WordofAdviceTV]

Happy to hear that the explanation was easy to follow. Thank you!

[@aqilshahkhan5179]

Goog job bro

[@paulvu7189]

Skilly technician 👍

[@WordofAdviceTV]

Thank you! 😄

[@melecioenciso6182]

Thanks man

[@AMe-nv4bo]

Thank you

[@Michael-mq3yi]

Hey Jay, I'm having a problem with my Kennmore HE 110.26002012. It's making a rubbing noise during the spin cycle with a load of clothes. Saw your vids on washing machine repair and you seem pretty knowledgeable. Can you help? Thanks

[@albodss]

The best video ever 🎉

[@WordofAdviceTV]

Thank you! 🙂

[@ninganpgh]

Funny and educational 👍👍👍😂😂😂

[@emisaelortega]

I have a question, can you add a vfd device to the home ac/furnace unit to increase the speed of the blower fan?

[@kevinklassen8199]

Hi there. I have a small round vent hole cut in the heat plenum just above my natural gas furnace. It is an American standard freedom 80. Can you tell what this is for?

[@billriga2825]

Question, I have Goodman 80+ gas forced air furnace. It runs for about 8 to 10 minutes on initial start-up. Then the inducer motor shuts down, main blower continues to run. 1 to 2 minutes later the inducer starts back and the furnace fires. Can I connect the continuity meter to the high limit switch while the furnace is running to see if the high limit is the cause of the inducer shut down and restart. Thanks for any information you have, videos are great.

[@mansurniazz]

Thank u very informative

[@WordofAdviceTV]

Glad you found it useful, thanks for stopping by and leaving a comment!

[@alboogie9508]

Hey, great video on November 28 my furnace went out and I have two resettable switches and it was flashing four times which is a code four, a limit circuit fault. I reset the switch and after three hours the furnace came back on and started heating up the house 13 days later it did it again and I watched your videos about the 10 things I could go wrong and I cleaned the flame sensor and the igniter. Put everything back together and 13 days later it went out again. Does that still mean that my heat exchanger is bad? Your videos are super helpful. Keep up the good work.

[@ninganpgh]

Is the little switch attached to the exhaust duct also a limit switch? Thanks!

[@johnpejakovich8848]

Good video

[@WordofAdviceTV]

Thank you John!

[@gulfjobsandNews]

I am watching from QATAR

[@PMartian]

Aloha! Can control board failure cause high limit fault? Recently changed high limit switch, flame sensor switch and still has high limit fault. Bypassed high limit switch and it still faulted. Replaced Control Board and now seems to be working fine? Can a Fan Limit switch cause a high limit fault? Thank you again as always.

[@Kids_Very_Fun]

Hi J can you please explain about heat pump please.

[@alexandrostapantaola191]

Can you do some videos on boilers and how they work?

[@tdngaymoibatau8269]

Please, make a video “how to calculate capacitor sizing for single phase “? Thank your!

[@sonle-fz1xb]

Son Le Thank you very much.

[@WordofAdviceTV]

You're welcome! Thanks for stopping by, have a great weekend!

[@Real-yo4eu]

So my furnace is giving some heat but not a lot and after about 4-5 mins the fire goes off then restarts afterwards. I noticed when this happens the heat sensor is heated red. I also already replaced the filter a couple days ago what’s the problem sound like?

[@user-or1uu7yt9n]

I just fixed a high limit to detect over temp from the heat exchanger and didn't actually think that was the problem until I checked ohms on the switch itself . It was weak and was short cycling so I put a new one in and everything has been good to go ! Just a warning from me to you . Get a good quality carbon monoxide detector installed in your homes because a heat exchanger that is cracked could kill you if carbon monoxide levels get too high in your home . And they are inexpensive .

[@frankjames1955]

hello, i have a code on my furnce that reads its the .. Limit Circut Fault ..i want to check the wire going to and from the saddle on the control board for this limit circut.. is this the red wires ?

[@OshonaikeGbenga]

just had my furnace inducer motor and thermostat newly changed, the flame sensor had been cleaned twice yet my furnace will work, and cut off before reaching hot or desired temperature. What can i do or check again?

[@ronamo111]

explain this one if you can i came home one night and my house was probably 250 degrees i hurried and opened all the windows and unplugged the thermostat. The next day i replaced the upper limit switch and everything was good. shouldn't the thermostat have shut down the furnace? If i had not come home when I did my house would have burned down.

[@tarikpompy8984]

I'm glad your back . How is life in Hawaii.

[@WordofAdviceTV]

Thank you! Hawaii life is definitely warmer than Minnesota life 😄 We are loving it!

[@calderart]

Can I bypass the condensate trap in my furnace by draining directly outside? The hose from the condensate trap goes though the floor to under the home into the crawl space anyway.

[@RG769]

Jay are you in Hawaii now? Did u finally moved over there doesn't look like Minnesota?

[@michaeltrowbridge7174]

Will this make a furnace keep running

[@drjahanzebamerica6922]

Cool

[@ittech7967]

I have Trane XB80 f.a.g.heater flashing codes say bad hight limit but the 3 thermostats have continuity & it wont fire up, Help!

[@HsingSun]

Thank you very much for your video. Is the thermal limit switch has nothing to do with cooling system?

[@WordofAdviceTV]

You're welcome! Yes, the thermal limit switch has nothing to do with the cooling system. 👍

[@jimbarron8688]

Hahaha... sometimes an overheating condition and faulty limit results in a plastic A/C condensate tray melting. Come cooling season you understand that a faulty limit and poor air flow can have consequences in the summer months. Dripping water onto the gas control will also provide for more fun come the cooling season. Fun and games.

[@jpol3808]

Hey Jay. Great video. Do one like that for all the furnace parts! I got a quick question for ya. When a limit switch has reached its life expectancy and has finally stopped working, would it be safe to say that it has finally reached its Limit? Lol. Got ya. Later. Jpol.

[@WordofAdviceTV]

Lol, I totally didn't see that one coming. Good one! 👍👍👌👌 I got a taste of my own jokes 😂

[@gregorycox7504]

if i change my over heat limit switch and accidentally cross the 2 wires, would it cause my blower to come on first then the inducer fan?

[@marcelopretti2398]

So the higher the upper limit of the switch the warmer the air will be flowing at the home? I mean a 200-40F will keep burners running longer than a 185-40F switch?

[@zekenzy6486]

Great Video. Have A Nice Weekend. Thank you for sharing ^_^. If possible Could you make video how to lubricate oil , grease on motor or hvac-r system. Thank you ^_^

[@WordofAdviceTV]

Thank you! If I come across a good motor for a video like that, that sounds like a great idea!

[@ReubenSahlstrom]

Neat video Jay! I think the temp gun you're using wouldn't measure the temperature accurately because it measures an area, rather than a point. It puts out some sort of infrared cone and measures a larger or smaller area depending on how far you hold it from the target.

[@WordofAdviceTV]

Thanks Reuben! Yeah, after I tried using it I had the same idea. That this type of temp gun is not a good choice for this experiment. Should have looked into it better 😅 Thanks for explaining how it works though! 👍👍👍

[@MrGattor33]

Very interesting video. My question is; what causes it to short cycle? Sorry but I don't recall seeing the explanation in the video. Is it because the limit switch has gone bad or what? Thanks for the video by the way!

[@WordofAdviceTV]

Thank you! A limit switch rarely goes bad, if it is opening it usually means there is a reason. Such as a dirty filter or a bad heat exchanger in a furnace. This video was more on how the switch works not on troubleshooting and figuring out why it opened. That's why I referenced my "10 reasons why a furnace overheats" video. In that video I go over the different reasons that would cause it to open.

[@MrGattor33]

@@WordofAdviceTV ah okay, now that makes sense. I personally wasn't looking for a fix but was just trying to understand this a little better. Thanks for the response and clarification!

[@dalenjurgens6751]

It's almost snow time in wyoming. I am desperately trying to figure out if it's a limit switch problem or flame roll out problem. It runs fine sometimes, then i just push reset on flame roll out. Runs fine for a couple cycles then cold air again. Help please. Thank you for the explanations. Learning more every winter. Lol

[@dalenjurgens6751]

Also i have L175 40F switch.

[@calderart]

I have the little beige one with the button reset. My furnace has been igniting the first burner and failing to start the other two. However, it does intermittently succeed. I've cleaned the flame sensor, the burners and cleared out all the debri in the burner box. I took the burners out and blew out the fuel path between them. They all appeared clean to start with. The furnace is only two years old. The exhaust pipe (PVC) is the Diversitech CVENT. So I don't know how to see inside the exterior pipe. The centre pipe looked clear but I could see water at the very bottom. Is that normal? A 'P' trap maybe? There is nothing covering the centre pipe. Should there be? After all the cleaning and reassembly now the furnace is short cycling. Perhaps just replacing the high limit switch and flame sensor is the next step. With that in mind my furnace is using propane so are there different switches and sensors that I should replace them with? You are the most professional and knowledgeable presenter that I've found on KZbin so I'm hoping you will have the insight I need. Thanks so much for your hard work in posting these videos.

[@calderart]

The limit switch continuity test passes. Also, would closed vents affect the startup? My boys often cover their vents.

[@jasonfoxfire]

My furnace was having the problem. I replaced two sensors like this and fixed it. If it is not the Nest controller, I wont even notice it is short cycling.

[@fyaglidere]

I have this Carrier gv3aav and my inducer motor turns on for a hot second then nothing.. I get error code 31 and I noticed the inducer motor gets 5v then drops to like 3v. Any idea why that might be happening? There's no capacitor only a big one on the other motor.

[@WordofAdviceTV]

That sounds like it could be a stuck pressure switch problem. I would suggest starting with this video and seeing if any of the presented problems are what you are experiencing: kzbin.info/www/bejne/kJLbYWWfqb57obc

[@dcmarvelunited5529]

How cold does it get in Hawaii? I'm in Chicago and it's a windchill of negative 8. Its dry in the house so I got the humidifier going

[@WordofAdviceTV]

Ahh yes.. I don't miss that kind of winter. Sounds chilly! Here in Kailua-Kona, Big Island winter gets to about 65F during the night and highs of 80 during the day. No HVAC at all in the house. Just ceiling fans and open windows.

[@dcmarvelunited5529]

@@WordofAdviceTV wow that sounds nice but doesn't that leave you with less hvac work

[@WordofAdviceTV]

@Dc Marvel United It's a little easier for me since I am not dependent upon HVAC work for my life expenses. Meaning even if I don't do any repair work for a while, I would be fine. I have a monthly KZbin income and I am into investing and day trading crypto currencies. That is more than enough for our family 🙂

[@dcmarvelunited5529]

@@WordofAdviceTV That's awesome, I wish you great success, wisdom, and health.

[@WordofAdviceTV]

@Dc Marvel United Thank you! 🙏🙏 I wish the same for you, multiplied!

[@mikeeeeee555]

My Goodman is short cycling 4 red lights. I’ve replaced the primary limit switch and the resettable rollout limit switches. Interestingly enough the system runs fine without the filter. Ive been using the least restrictive basic merv1 or merv2 filter and still have the issue. The furnace is only two years old. It’s driving me crazy!

[@WordofAdviceTV]

Hey Michael! Sorry to hear about the furnace troubles. Have you watched my video where I go over 10 reasons why a furnace can overheat? kzbin.info/www/bejne/aYuznp-qibdoiZY Another option would be to increase the blower fan speed if that's possible on your unit. Set the heat speed from low to medium. I go over blower motor wiring in this video: kzbin.info/www/bejne/aoSbhY2aYplomLs

[@mikeeeeee555]

@@WordofAdviceTV thank you for the reply! Is it safe to increase the blower speed? Eg. Is blower speed adjustment a common fix for the issue I described? The wires from the blower motor connect to terminals on the board marked T1 T2 T3 T4. Then there are a bunch of dip switches that need to be configured, so appears somewhat complicated... My unit is Goodman gmec960603bnab.

[@WordofAdviceTV]

@@mikeeeeee555 In most cases increasing the blower speed is a valid solution and does not have any repercussions. Usually I would only do this after I checked everything else though. If everything seems normal yet the unit is still overheating, then I would try to increase the fan speed. Going from low speed to medium speed is not a big difference but it may be enough to stop the problem. But being that the unit is only 2 years old, I find it odd that it is overheating. It wasn't overheating last year right? So I wonder what changed between then and now.

[@mikeeeeee555]

@@WordofAdviceTV the house was built two years ago. I’m a new owner and this was our first winter. Not sure if I inherited these issues. Thanks for the video link. My system has all of the motor wires connected to main board and a bunch of dip switches that I think need to be adjusted. Perhaps a bit more complicated on my system.

[@WordofAdviceTV]

@Michael Shifrin Ah I see.. That makes it a little harder. If you happen to have a variable speed motor (it has like 16 wires going from it), with those motors one can't change the speeds. If you have the installation manual from that furnace (or perhaps can look it up online), they should have a section in it that explains what all the different dip switch positions mean.

[@timothyandersen1533]

Do you need to replace your furnace limit switch with an exact replacement? Or same type and temperature settings good enough?

[@WordofAdviceTV]

In most cases, one that looks similar and has the same temperature range is good enough. No need to do get the exact replacement, especially if it costs 4 times as much.

[@harrydickson4575]

👍👍👍

[@WordofAdviceTV]

Harry, you are appreciated man!

[@kevintimothyshields]

Will a furnace sometimes employ a limit switch to confirm the existence of heat? I.e. "Set a timer and check the status of this limit switch. If within N seconds the switch remains open this means there is no heat.... so turn off the inducer and then try again in 90 seconds."

[@Eddy63]

Hey Jay , good demo ... And if those batteries weren't free , how much would you ''charge '' for them ? Lol ... Aloha ...

[@WordofAdviceTV]

Heheh the battery jokes continue 😄 Thanks for stopping by Eddy, hope your weekend is off to a great start!!

[@davidmckinney6577]

Hello Eddy ✌️🤙🤟

[@ryk1265]

Just make sure they're actually free, because if you steal them and you get caught you'll be immediately "charge"!

[@duke-.-]

Could you do another rummikub vid on how to win 99% of the time?

[@hvactech5829]

I see your face everyday :)

[@davethomas6800]

Hey Jay, Your instructional videos are incredible! My Dad and I have used them for troubleshooting for AC & Furnace issues. Question... We have been trying to diagnose a short cycling furnace problem for a couple days now. It will ignite, light and then go out anywhere between :30-3:30min and then cycles again, have to reset furnace with switch after 3-4 times. I have an 15 yr old American Standard High Efficiency Gas Furnace (AUX 1C100A9481AA). The diagnosis light is blinking normally. We have bypassed the Upper limit switch, filter is new, checked the vent, cleaned the burners, no drain problem, made sure the flame thermocouple is placed & working correctly, flames burn blue and perfectly draw in, checked all electrical connections are tight, bypassed all three limit switches, one at a time, and doesn't change the cycling, checked that PVC vent is angled upward correctly, and probably see other items... I thought I would make one last ditch effort to reach out to you and your community before we throw in the towel and pay the piper. Thanks in advance for any suggestions you all have!

[@davethomas6800]

This afternoon we did something that is finally getting it running past the 3:30min and staying on. Not really sure what I did to fix it though??? I ended up cleaning a very small amount of debris from the outside (side of the house) of the exhaust PVC. It sure didn't seem like a lot, but maybe. Also, I disconnected the exhaust vent PVC inside the house for a few minutes to see if that change in pressure would keep it going, thinking there may be a restriction in the line, but it ended up stopping before the igniter even glowed and cycling again. In the process of disconnecting the exhaust inducer I had to loosen all the inducer screws and move the inducer to disconnect the exhaust vent PVC. Well after all that, now the heat stays running. I know the pressure sensor is extremely sensitive, so maybe getting rid of some little restriction in the exhaust PVC did the trick?? Thanks for your replies and cross your fingers for me that it stays working :)

[@gjuelz7672]

@@davethomas6800 your AC evaporator coil is clogged. Check KZbin videos of clogged AC evaporators coils. They get gunked up with debris and prevent your furnace from blowing air through it efficiently. They get so clogged that they restrict air flow, and your furnace overheats because all the hot air is trapped where all the sensors are, causing them to trip! Make sure you look at the INSIDE of your A.C. evaporator coil, by the way. The OUTSIDE of the coil will always look clean, so you need to inspect the INSIDE. Reply to this comment if you end up checking the evaporator coil and cleaning it...curious if it will fix your issue.

[@terryrobinson3624]

Does it matter which contact you hook your meter to

[@WordofAdviceTV]

Some people say black needs to go to common but as far as I know it doesn't matter. I do it both ways, just whatever lead gets there first 😅

[@BigThomTattoos]

I have watched many of your videos and have replaced ever limit switch and it is still keeps kicking off before the heat comes on

[@WordofAdviceTV]

Sorry to hear about the furnace troubles. How far in the sequence of operation does it get? Does the blower motor come on? Does the board blink some error code when it shuts off? (sequence of operation: kzbin.info/www/bejne/d4KnkICbma6eoqs )

[@BigThomTattoos]

@@WordofAdviceTV can I DM you on Instagram or Facebook?

[@jimtwisted1984]

You fix furnaces in Hawaii and i fix air conditioners in Alaska.

[@WordofAdviceTV]

That sounds about right 😇

[@doctor9768]

Hi Jay, My Goodman Furnace, GMSS96 will not heat with a filter installed with a Merv rating greater than Merv 2. Getting 4 flashes from the red LED. (Primary Limit Switch Circuit) Goodman's tech support recommends a Merv of 8. Replace the 8 Merv with a 2 Merv, all is good. Any thoughts on this? Any viewers have the same issue?? Thank you all....

[@Sesamestreet9080]

Check blower speed

[@doctor9768]

@@Sesamestreet9080 Thank you. The blower speed escaped me🤔 Thanks for the continuing education!😁

[@Sesamestreet9080]

@@doctor9768 no problem. Also check the coil if that’s caked up with dust that also can cause airflow restrictions

[@blitzblutz]

Is there any need for a furnace guy in the South Pacific?!?

[@WordofAdviceTV]

Haha not really 😄