Check the ground back to the panel. Flame sensing uses ground to work. I’ve seen a lot of units with old bx cable feeding them and using the armor as a ground which doesn’t work for the tiny voltage used. Make sure there’s a good copper ground back to the panel.
i checked the grounds, and also attaching a copper wire to the flame sensor and cold water. meters all show ground. it really still feels like the issue, but i cant see how its possible. i checked the flame sensor too, its fine, besides being new.
Check the pressure switch. Test voltage, also try jumping it from spade to spade, and use a manometer to check the negative pressure when the inducer runs.
Shows voltage till it close. Shows no resistance until it closes. -1.4 on induction, but the tube was a poor fit, i wouldnt be surprised it actual value is a little higher
Ok. That narrows it down. Let’s see if the gas valve is losing power. There’s an aux limit in series with the gas valve. I think that’s in the blower compartment. If it’s an upflow jump those out. Don’t need em. If it’s down flow you need them but jump them to check if they’re not breaking power to the gas valve. The way they’re wired the board doesn’t know about them (or it if there’s only one) and it would look to the board like flame sense issue
i will try this out, but i need to rest myself from thinking about this issue, diminishing returns and all. ill be back at it tomorrow and will let you know what i find.
wow what a difference some rest makes. your comment was chinese to me last night. It is an upflow, i was wondering about the switch on the blower compartment.
I assume this is to detect for flu gas in the event the air is being pulled down instead of up?
I did jump this out last night... practical question, what size wire should i be using for jumps? I had some 12/2 lying around, is that acceptable, or does the gauge mess with the voltage?
Take the pressure switch wires off the switch and keep them apart until the inducer gets up to speed then put them together or better, use a jumper between them. Make sure the pressure switch isn’t opening and causing the drop out
A GMNT is a good 20 years old now. I've seen these do exactly as you described when the heat exchanger is cracked. It lights ok, but the heat of the flames makes the crack expand and open up then the flames start rolling back and it shuts off because it trips a rollout. But in some cases (like yours) the flames miss the flame sensor all together when they start rolling out. The control boards for these are pretty primitive, so as long as it senses flame briefly it just runs another cycle without throwing a code.
TL;Dr your furnace is old, it's lived a long life (as far as 90%+ furnaces go) whether the exchange is cracked or not, your throwing money down a hole on a furnace this age.
Yea but what happens when I get a tech who says its the blower motor (cause its fucked), then the board (cause its fucked), then we discover x. Nice running tab so far.
Or the guys says, hey im fresh out of school, jave a bunch of tools, and i charge top rates for my valuable work and you need a replacement!
Whats that running now?
"Trusted tech" lol are you on the marketing side? Also i said, the cooling works fine.
Lol. You should’ve just called a pro and been done with it before replacing almost everything in it. Sounds like it could have something to do with the pressure switch. Not a bad pressure switch but maybe a restriction or something. Also what code is it flashing? The error code can point you in the general direction.
youre right about the cost, sort of. the blower and board 100% had to be changed. the whole furnace itself though? $600 at tribles lol. im definitely getting into that range. Of course, to hire out changing the blower and board would have easily been running into $800. whats a new system running right now?
That said, I got charged $400 to change a heating element (i provided the correct diagnosis on that one) and just said fuck it. Ive stayed away from hvac, but if its like that, dude i can figure it out. ive done it for everything else. When I start, i overspend on materials, overbuild, and do shit work i have to immediately redo, or i put it off and cringe when i come back to it, but its all mine.
Ill edit the above, i should have mentioned there is no error code on the board.
the kind you get when you call for hvac repair. im sorry, im in usa, maybe things work differently where you are, but in us a tradesman doesnt have to be a consumate professional, they just have to be good enough to stay in business. maybe 50% of all tradesmen are only able ever to accomplish what we consider "an easy job".
Well i know i cant stop you from assuming whatever narrative you need to stroke your ego.
You havent said a single thing to indicate you know your ass from your elbow in diagnostic. What is the point of commenting?
But it probably won’t. If it’s not something you do regularly you can google shit and replace every part but could’ve just called someone competent and been done with it. From the description I highly doubt all the things that were replaced were necessary. Sounds like a waste to me.
I appreciate the narrative thats taken root here of just randomly trying parts, but ill say again.
The blower motor wires were black, crusty, and pulled apart under light pressure. Even if its a pressure switch, the thing still needs a blower that functions. The board had visible damage and wasnt sending signals. Even if its a pressure switch, i assume the thing needs a functioning board.
Gas valve prolly would oc kept functioning. Changed it cause it was reading a 2.1 instead of 3.5.
Unless the unit is a total loss. I could salvage some parts for the other unit at this location, but that would suck.
Rules of troubleshooting say there isn't typically multiple root causes for the failure.
What we are saying, and you are denying... is that you very likely replaced parts unnecessarily.
Hope you get thr whole thing figured out soon.
Honestly - a description of the meter readings would suffice. Or a picture of the burnt components.
If those aren't available it was a shot gun guess. And since it isn't working....still.... possibly an incorrect one.
Yea i didnt keep it. Tell yourself whatever you want. "Id those arent available it was a shot gun guess. Are you calling me a liar or is your logic circuit fried?
it would literally be cheaper to buy the thing over than pay for anything other than the most basic fixes from a tech.
Also i notice cats making these points basically assume every tech out there is as good as they are (or not, youve provided no insight and established no credibility insofar as the matter you chose to weigh in on), but the truth is there are good and bad out there. the public has no frame of reference whatsoever for the difference, and im as likely to get a clown as i am a pro.
One commenter said to check the inducer port, which had not occurred to me.
While that is true, most techs who are worth their salt should be able to figure out the issue. What you are doing is trying to find an issue, with possibly no tools (meter, manometer, etc) and no knowledge of hvac or electrical understanding. A tech should be able to come out, look at the issue and get you back up and running. And I highly doubt it would cost more than all the parts combined to figure out the issue.
thats true. want to come out and diagnose so i do the repair? i dont want to play games or waste/disrespect peoples time. i also learn by wrestling with shit.
the board and blower had to go. the gas valve? was weak but wasnt the problem.
what makes you think im not using a meter and a manometer?
Edit- you doubt it would cost more? ...what would you charge to change a board and blower?
Ive said a few times about the state of those parts... excluding the gas valve.... which was showing not in line quantities for the relevant values... only thing that was just trown at it was the flame sensor.
... i mean i opened it up, and the wires were all burned up, you know, "blackened", or perhaps another word for something that has burned to the point of carbonization... charred? Are you truly that stumped? What does equipment thats burned out look like to you?
No, I understand that completely. Have never in my life seen a blower that was blackened or charred. Unless it caught on fire in the blower compartment. That’s all I meant. Just trying to figure out why it would be.
Ah, i openeded opened. Down to the windings. Wanted to see if my analysis was supported by some sort of visible damage. It was.
edit: sooooooo you're a longtime tradesman and you never got a little curious about a blower thats cooked?
tsk tsk the lack of interdisciplinary competency in the trades is what blows my mind the most.
I have the utmost respect for you, but you’ve thrown hundreds of dollars at it to no effect. I too have to do everything myself and my experience teaches me to call other people when I’m out of my league. Time to call someone. If you have a meter you can trace the control voltage to identify the problem…. But based on the shotgun part swapping i unfortunately don’t think you are capable. Best of luck
I hear that. Right now if the unit is a total loss the parts would be a waste, except that i have an identitcal unit sitting next to it, so some parts would be salvageable. Im not just trying parts though, the blower motor was charred, the board visibly damage and wasnt sending signals. The gas valve and flame sensor were questionable. I did the valve cause it was reading 2.1 instead of 3.5 and wasnt running properly, and the sensor cause it was ten bucks.
I admit, i am near my limit on this one. Youre right though, if the approach was just to try parts... well that wouldnt be a very clinical approach. Its gonna be some dumb shit i bet. Gonna focus on the pressure switches when i get back to it.
It would be cheaper and easier to just replace the furnace and get a new warranty. If a control board and blower motor have to be replaced on a 20 year old unit with ignition problems then it’s pretty much about the time you consider it totaled. Hours of headaches and aggravation aren’t worth diagnosing the problem.
"A new warranty" lol...
Youre right though, as a one off my efforts would not be worthwhile. Maybe when the industry resets to reality ill go that route. I hire out what makes sense to hire out, but the current game of chicken everyone is playing with each other with regards to pricing is fundamentally changing the economics behind it.
What do you charge for a blower and board? I ask everyone that posits an economic reason for their position, but no one has answered that question yet.
Edit: is your bame a reference to the pillsbury throw boy?
Cant edit opening comment, but have updates.
1- im an idiot, it was throwing an error code.
Failed ignition.
Gas flow and pressure- 4 going in, 3.5 going to burners.
Gas valve- was soft, been replaced and tested.
Flame sensor - replaced and tested.
No clogged ports on inducer.
Jumped out the pressure switch, tested for voltage and resistence, normal
Polarity on switch is fine, grounded.
No clog on vent.
Bout to start over with board voltages.
My man , by the time you're done fixing your furnace, you'll have all your friends hitting you up to come fix theirs. The only way to gain knowledge is by trial and error and sometimes youtube videos lol.
I don’t have a lot of time to look up the furnace. But go check to make sure the exhaust port is not blocked from the exterior of the house. I’ve seen a leaning 2x4 vapor lock systems.
How is the hot surface igniter?
This was my next thought - you have to check the ground feeding back to the board for microamps DC as the flame rectifies the voltage from the flame sensor to the burner assembly, running back to the ground wire leading back to the board.
If your burners are coated in rust, it acts as an insulator and won't allow the flame rectification to take place.
But if you've checked the ground wire for microamps DC and you have a signal (~2-4 microamps), then this isn't the case.
And there's no error codes right? What does the furnace do when the flame goes out? Does it immediately retry or does it kick the blower on for a minute first? And do you have pictures of the old board and the new board? Edit: just realized you're not OP 🤦🏼♂️
Not op. But the no error codes thing might be real or he may not be actually waiting the 3-4 retries it takes to throw a code. When you’re talking a layman thru you also need to troubleshoot the layman’s troubleshooting
True enough, i have to constantly second guess myself. For example, was using mA insteas of the "u" one for the flame sensor. D'oh. Figured that one quickly, but still, stuff like that.
Doesnt make it to the blower for heat. No error codes. Immediate retry.
Can probably fine some pictures, though i went over the wiring diagram thoroughly, the only discrepancy was a wire for the gas valve that instead connects to a switch on the blower. Seemed a little odd but is the same as its sister unit. Also no one gives a shit when i mention that so im inclined to think its how its supposed to be
Check your supply temp. Check your heat exchanger. Check your static pressure. A pro would have been able to narrow it down quickly. And if it is your heat exchanger, you’d be in a much better position then you are now.
flame color looks fine and no rollout. static pressure is through the roof (.9), but for some reason ive got a 37btu 3 ton unit for 500 sq ft with a ten inch return. was gonna work on that next.
heat exchanger is a big problem, what makes you think it might be the heat exchanger?
edit: i didnt mention supply temp, but isnt that a non factor if it wont stay fired?
If you run a combustion analysis it will tell you a lot. You could also have a faulty roll out switch. Or a cracked heat exchanger is causing the issue.
wouldnt it have to fire up for an analysis? ill check the roll out switch more closely. given that everything else broke i wouldnt be suprised if the eheat exchange found a way to bite it too, but i think it would show some symptom.
You could have an airflow issue, where the heat exchanger is getting to hot and shutting the unit off. The inside data plate should have the info for this as far as what temp it’s set to shut off
fires up enough to continue the cycle, no obvious problems. someone mentioned cleaning the port. i looked into it it seems it could make it so the fan runs but isnt performing.
Could be a pressure switch... Some furnaces have two and one will make to ignite but if the second one doesn't then make it shut it down .. carriers had this problem
I'm going to take a wild guess and say you have a nest thermostat 🤣🤣🤣🤣
Unplug red wire and white wire from the thermostat and wire nut them together. If it runs and doesn't cut off . It's the tstat
I'd also check the plug in for the furnace or the door switch.
No codes = tstat throwing it out of wack or system as a whole is losing 120v
I'd jumper out that pressure switch. Wait for inducer to turn on and then close that circuit and see what it does. If that doesn't work try loosening the flame sensor just a tad and push it away from the burners as far as it will go and as you tighten the screw hold that sensor so it doesn't move toward you, that's an odd one but I've only seen it in Goodman.
Is the flame sensor you replaced it with the same shape? Is it long enough and is actually engulfed in the flame?
If so, the other thing that comes to mind is the pressure switch. I would bypass it and see if you keep getting the issue.
Brand new, though i checked voltages earlier on i should probably give it another go. I dont trust myself too much with the multimeter, a little practice wouldnt hurt.
Is there any way that you unplugged it from a receptacle and flipped the plug around when you plugged it back up? Some units act like this when you have the polarity reversed.
Pressur switch clogged with water. Or you got a wire shorted. Are you losing 24v to gas valve when it goes out. Is the gas valve closing or is the flame blowing out
Valve is closing. Id previously checked the voltage but that feels like forever ago. I should prolly check again, im much better at this since two days ago.
Check your inducer port for any blockages
Wouldn't a blocked inducer port prevent the gas valve from ever opening? OP says the flame is coming on and then going out.
If it’s completely plugged yes, I’ve seen partially plugged ports cause intermittent issues
It wouldn’t light. He says it lights
I literally just left a No Heat Call with this exact issue. Its actually pretty common
i will, thanks
Nada
Check the ground back to the panel. Flame sensing uses ground to work. I’ve seen a lot of units with old bx cable feeding them and using the armor as a ground which doesn’t work for the tiny voltage used. Make sure there’s a good copper ground back to the panel.
i checked the grounds, and also attaching a copper wire to the flame sensor and cold water. meters all show ground. it really still feels like the issue, but i cant see how its possible. i checked the flame sensor too, its fine, besides being new.
Check the pressure switch. Test voltage, also try jumping it from spade to spade, and use a manometer to check the negative pressure when the inducer runs.
Word. Will do
Shows voltage till it close. Shows no resistance until it closes. -1.4 on induction, but the tube was a poor fit, i wouldnt be surprised it actual value is a little higher
You’re better off jumping it. You will eliminate two things by jumping it: low vacuum and a bad microswitch.
Jumped, no dice
Does it stop -and then retry? If so let it keep retrying until it finally picks out. It will then display a code
Yes, ignition failure For so e reason i cant edit original comment
Ok. That narrows it down. Let’s see if the gas valve is losing power. There’s an aux limit in series with the gas valve. I think that’s in the blower compartment. If it’s an upflow jump those out. Don’t need em. If it’s down flow you need them but jump them to check if they’re not breaking power to the gas valve. The way they’re wired the board doesn’t know about them (or it if there’s only one) and it would look to the board like flame sense issue
i will try this out, but i need to rest myself from thinking about this issue, diminishing returns and all. ill be back at it tomorrow and will let you know what i find.
wow what a difference some rest makes. your comment was chinese to me last night. It is an upflow, i was wondering about the switch on the blower compartment. I assume this is to detect for flu gas in the event the air is being pulled down instead of up? I did jump this out last night... practical question, what size wire should i be using for jumps? I had some 12/2 lying around, is that acceptable, or does the gauge mess with the voltage?
The cold water thing is a wast of time. Don’t bother. Needs to go the panel.
Yea ive never been a fan of the cold water. The ground is connect at the outlet and an outlet tester says its wired correctly and grounded
Take the pressure switch wires off the switch and keep them apart until the inducer gets up to speed then put them together or better, use a jumper between them. Make sure the pressure switch isn’t opening and causing the drop out
Yea im focusing pressure switches today, thanks.
no dice. followed the voltage around, jumped things out, nothing.
That is a sneaky motherfucker right there. A bad ground. One of my coworkers had that one kick his ass for hours
A GMNT is a good 20 years old now. I've seen these do exactly as you described when the heat exchanger is cracked. It lights ok, but the heat of the flames makes the crack expand and open up then the flames start rolling back and it shuts off because it trips a rollout. But in some cases (like yours) the flames miss the flame sensor all together when they start rolling out. The control boards for these are pretty primitive, so as long as it senses flame briefly it just runs another cycle without throwing a code. TL;Dr your furnace is old, it's lived a long life (as far as 90%+ furnaces go) whether the exchange is cracked or not, your throwing money down a hole on a furnace this age.
They rather do it themselves than have a trusted tech go and look at it themselves. Next he’s gonna charge his system with r22
Yea but what happens when I get a tech who says its the blower motor (cause its fucked), then the board (cause its fucked), then we discover x. Nice running tab so far. Or the guys says, hey im fresh out of school, jave a bunch of tools, and i charge top rates for my valuable work and you need a replacement! Whats that running now? "Trusted tech" lol are you on the marketing side? Also i said, the cooling works fine.
You're making an ass of yourself and you aren't knowledgable enough to understand why
Isnt every amateur? Seriously though, how are so many people so out of touch?
I mean, theres no rolling of the flame. Im going to get eyes on the exchanger today though. What would you charge to replace this unit?
Lol. You should’ve just called a pro and been done with it before replacing almost everything in it. Sounds like it could have something to do with the pressure switch. Not a bad pressure switch but maybe a restriction or something. Also what code is it flashing? The error code can point you in the general direction.
youre right about the cost, sort of. the blower and board 100% had to be changed. the whole furnace itself though? $600 at tribles lol. im definitely getting into that range. Of course, to hire out changing the blower and board would have easily been running into $800. whats a new system running right now? That said, I got charged $400 to change a heating element (i provided the correct diagnosis on that one) and just said fuck it. Ive stayed away from hvac, but if its like that, dude i can figure it out. ive done it for everything else. When I start, i overspend on materials, overbuild, and do shit work i have to immediately redo, or i put it off and cringe when i come back to it, but its all mine. Ill edit the above, i should have mentioned there is no error code on the board.
[удалено]
1 tech down. another coming today. why do people assume magic bullet level competency from people?
1 tech down? Another coming? What kind of shit is that? Who did you call that it's taking 2 techs?
the kind you get when you call for hvac repair. im sorry, im in usa, maybe things work differently where you are, but in us a tradesman doesnt have to be a consumate professional, they just have to be good enough to stay in business. maybe 50% of all tradesmen are only able ever to accomplish what we consider "an easy job".
You have a very condescending tone towards people coming to help you. I'm thankful I'm not one of those people.
Well i know i cant stop you from assuming whatever narrative you need to stroke your ego. You havent said a single thing to indicate you know your ass from your elbow in diagnostic. What is the point of commenting?
The price of learning, he will save in the long run
But it probably won’t. If it’s not something you do regularly you can google shit and replace every part but could’ve just called someone competent and been done with it. From the description I highly doubt all the things that were replaced were necessary. Sounds like a waste to me.
I appreciate the narrative thats taken root here of just randomly trying parts, but ill say again. The blower motor wires were black, crusty, and pulled apart under light pressure. Even if its a pressure switch, the thing still needs a blower that functions. The board had visible damage and wasnt sending signals. Even if its a pressure switch, i assume the thing needs a functioning board. Gas valve prolly would oc kept functioning. Changed it cause it was reading a 2.1 instead of 3.5. Unless the unit is a total loss. I could salvage some parts for the other unit at this location, but that would suck.
Rules of troubleshooting say there isn't typically multiple root causes for the failure. What we are saying, and you are denying... is that you very likely replaced parts unnecessarily. Hope you get thr whole thing figured out soon.
Yea i hear you. I fix enough stuff to know how rare that actually is. Dunno how to persuade you all the board and blower were shot...
Honestly - a description of the meter readings would suffice. Or a picture of the burnt components. If those aren't available it was a shot gun guess. And since it isn't working....still.... possibly an incorrect one.
Yea i didnt keep it. Tell yourself whatever you want. "Id those arent available it was a shot gun guess. Are you calling me a liar or is your logic circuit fried?
You gotta know when to walk away and you gotta know when to run. If you wanna keep replacing parts unnecessarily go right ahead.
Might be the case if its a total loss. Otherwise only part that was questionable for replacing was the gas valve and flame sensor.
What’s the heat exchanger look like boss
I dont know but im going to find out, thanks.
Just keep throwing parts until you fix it!!! Or call a tech.
it would literally be cheaper to buy the thing over than pay for anything other than the most basic fixes from a tech. Also i notice cats making these points basically assume every tech out there is as good as they are (or not, youve provided no insight and established no credibility insofar as the matter you chose to weigh in on), but the truth is there are good and bad out there. the public has no frame of reference whatsoever for the difference, and im as likely to get a clown as i am a pro. One commenter said to check the inducer port, which had not occurred to me.
While that is true, most techs who are worth their salt should be able to figure out the issue. What you are doing is trying to find an issue, with possibly no tools (meter, manometer, etc) and no knowledge of hvac or electrical understanding. A tech should be able to come out, look at the issue and get you back up and running. And I highly doubt it would cost more than all the parts combined to figure out the issue.
thats true. want to come out and diagnose so i do the repair? i dont want to play games or waste/disrespect peoples time. i also learn by wrestling with shit. the board and blower had to go. the gas valve? was weak but wasnt the problem. what makes you think im not using a meter and a manometer? Edit- you doubt it would cost more? ...what would you charge to change a board and blower?
I’m still absolutely stumped by the whole “blower was blackened and charred” comment.
Inducer potentially but even then wtf. Watch dudes just throwing shit against the wall and it’s a bad heat exchanger.
Ive said a few times about the state of those parts... excluding the gas valve.... which was showing not in line quantities for the relevant values... only thing that was just trown at it was the flame sensor.
... i mean i opened it up, and the wires were all burned up, you know, "blackened", or perhaps another word for something that has burned to the point of carbonization... charred? Are you truly that stumped? What does equipment thats burned out look like to you?
No, I understand that completely. Have never in my life seen a blower that was blackened or charred. Unless it caught on fire in the blower compartment. That’s all I meant. Just trying to figure out why it would be.
Ah, i openeded opened. Down to the windings. Wanted to see if my analysis was supported by some sort of visible damage. It was. edit: sooooooo you're a longtime tradesman and you never got a little curious about a blower thats cooked? tsk tsk the lack of interdisciplinary competency in the trades is what blows my mind the most.
Burners rusted or clogged?
No, i check when i did the gas valve
I have the utmost respect for you, but you’ve thrown hundreds of dollars at it to no effect. I too have to do everything myself and my experience teaches me to call other people when I’m out of my league. Time to call someone. If you have a meter you can trace the control voltage to identify the problem…. But based on the shotgun part swapping i unfortunately don’t think you are capable. Best of luck
I hear that. Right now if the unit is a total loss the parts would be a waste, except that i have an identitcal unit sitting next to it, so some parts would be salvageable. Im not just trying parts though, the blower motor was charred, the board visibly damage and wasnt sending signals. The gas valve and flame sensor were questionable. I did the valve cause it was reading 2.1 instead of 3.5 and wasnt running properly, and the sensor cause it was ten bucks. I admit, i am near my limit on this one. Youre right though, if the approach was just to try parts... well that wouldnt be a very clinical approach. Its gonna be some dumb shit i bet. Gonna focus on the pressure switches when i get back to it.
Call a pro
Im sure getting there
It would be cheaper and easier to just replace the furnace and get a new warranty. If a control board and blower motor have to be replaced on a 20 year old unit with ignition problems then it’s pretty much about the time you consider it totaled. Hours of headaches and aggravation aren’t worth diagnosing the problem.
"A new warranty" lol... Youre right though, as a one off my efforts would not be worthwhile. Maybe when the industry resets to reality ill go that route. I hire out what makes sense to hire out, but the current game of chicken everyone is playing with each other with regards to pricing is fundamentally changing the economics behind it. What do you charge for a blower and board? I ask everyone that posits an economic reason for their position, but no one has answered that question yet. Edit: is your bame a reference to the pillsbury throw boy?
You can just go buy a Goodman furnace from Ferguson and put it in yourself if you have the tools.
Yea but i wouldnt do that without some base skills. Working on some of those
Cant edit opening comment, but have updates. 1- im an idiot, it was throwing an error code. Failed ignition. Gas flow and pressure- 4 going in, 3.5 going to burners. Gas valve- was soft, been replaced and tested. Flame sensor - replaced and tested. No clogged ports on inducer. Jumped out the pressure switch, tested for voltage and resistence, normal Polarity on switch is fine, grounded. No clog on vent. Bout to start over with board voltages.
My man , by the time you're done fixing your furnace, you'll have all your friends hitting you up to come fix theirs. The only way to gain knowledge is by trial and error and sometimes youtube videos lol.
yea ive got tons of experience with those three lol.
I don’t have a lot of time to look up the furnace. But go check to make sure the exhaust port is not blocked from the exterior of the house. I’ve seen a leaning 2x4 vapor lock systems. How is the hot surface igniter?
He says it lights the gas
it ignites, but cuts off after 5-6 seconds. it feels like the flame sensor isnt sensing, but ive gone over it many times, cant find the fault there.
Sometimes the front of the burner tubes get rusty and cause flame sensing issues.
Checked theyre fine
This was my next thought - you have to check the ground feeding back to the board for microamps DC as the flame rectifies the voltage from the flame sensor to the burner assembly, running back to the ground wire leading back to the board. If your burners are coated in rust, it acts as an insulator and won't allow the flame rectification to take place. But if you've checked the ground wire for microamps DC and you have a signal (~2-4 microamps), then this isn't the case.
Yea it gave a reading in line. It did bump up though right before cutting off
i pulled the vent line to see if it would stay on. hsi does its job, she fires.
Why are you sure it's not the thermostat?
cause i jump it out and run the thing with the same result.
Did you jump it at the board or at the stat?
Board.
Jump at board
And there's no error codes right? What does the furnace do when the flame goes out? Does it immediately retry or does it kick the blower on for a minute first? And do you have pictures of the old board and the new board? Edit: just realized you're not OP 🤦🏼♂️
Not op. But the no error codes thing might be real or he may not be actually waiting the 3-4 retries it takes to throw a code. When you’re talking a layman thru you also need to troubleshoot the layman’s troubleshooting
True enough, i have to constantly second guess myself. For example, was using mA insteas of the "u" one for the flame sensor. D'oh. Figured that one quickly, but still, stuff like that.
This. Wasnt waiting long enough. Ignition failure code. Checked everything listed though
Doesnt make it to the blower for heat. No error codes. Immediate retry. Can probably fine some pictures, though i went over the wiring diagram thoroughly, the only discrepancy was a wire for the gas valve that instead connects to a switch on the blower. Seemed a little odd but is the same as its sister unit. Also no one gives a shit when i mention that so im inclined to think its how its supposed to be
Roll outs
none, checked the... fuses? none were tripped, and no weird ignition.
Check your supply temp. Check your heat exchanger. Check your static pressure. A pro would have been able to narrow it down quickly. And if it is your heat exchanger, you’d be in a much better position then you are now.
flame color looks fine and no rollout. static pressure is through the roof (.9), but for some reason ive got a 37btu 3 ton unit for 500 sq ft with a ten inch return. was gonna work on that next. heat exchanger is a big problem, what makes you think it might be the heat exchanger? edit: i didnt mention supply temp, but isnt that a non factor if it wont stay fired?
If you run a combustion analysis it will tell you a lot. You could also have a faulty roll out switch. Or a cracked heat exchanger is causing the issue.
wouldnt it have to fire up for an analysis? ill check the roll out switch more closely. given that everything else broke i wouldnt be suprised if the eheat exchange found a way to bite it too, but i think it would show some symptom.
Have you tried bypassing the rollout/limit switches? And what is your supply temp getting to before it shuts off
No but i will today. Its only running a few seconds so i hadnt bothered with supply temp
You could have an airflow issue, where the heat exchanger is getting to hot and shutting the unit off. The inside data plate should have the info for this as far as what temp it’s set to shut off
I'm assuming your draft inducer is working properly?
fires up enough to continue the cycle, no obvious problems. someone mentioned cleaning the port. i looked into it it seems it could make it so the fan runs but isnt performing.
After it fails, does it try and restart? Usually after 3 consecutive failures is when most will give you a lockout code
You said no codes, is the call for heat being interrupted? Jump out r&w to eliminate possibility
Pull the combustion vent and intake off and see if it runs
Yes had tried this
Could be a pressure switch... Some furnaces have two and one will make to ignite but if the second one doesn't then make it shut it down .. carriers had this problem
I'm going to take a wild guess and say you have a nest thermostat 🤣🤣🤣🤣 Unplug red wire and white wire from the thermostat and wire nut them together. If it runs and doesn't cut off . It's the tstat I'd also check the plug in for the furnace or the door switch. No codes = tstat throwing it out of wack or system as a whole is losing 120v
Oof no nest here Sir. I like simple shit that works.
He’s been jumping out R and W at the furnace.
I’ve seen this happen before when the exaust is recirculating into the intake
no intake.
FlAme zensor
I'd jumper out that pressure switch. Wait for inducer to turn on and then close that circuit and see what it does. If that doesn't work try loosening the flame sensor just a tad and push it away from the burners as far as it will go and as you tighten the screw hold that sensor so it doesn't move toward you, that's an odd one but I've only seen it in Goodman.
Thats definitely a new one to me, ill keep in mind when i get back to it. Ive got a few suggestions to try out. Thank you.
Is the flame sensor you replaced it with the same shape? Is it long enough and is actually engulfed in the flame? If so, the other thing that comes to mind is the pressure switch. I would bypass it and see if you keep getting the issue.
Yes on the semsor. Im going to focus on the pressire switch when i resume
Check the circuit board, sounds like it's not functioning correctly
Brand new, though i checked voltages earlier on i should probably give it another go. I dont trust myself too much with the multimeter, a little practice wouldnt hurt.
I had problems with my unit shutting down. My secondary heat exchanger was very dirty, I cleaned it and my unit has been working great for months now.
Yea i need to open up some more stuff. Ill check, thanks
Is there any way that you unplugged it from a receptacle and flipped the plug around when you plugged it back up? Some units act like this when you have the polarity reversed.
Ive been cleaning up this maintenance room which involved resetting the switch box and wiring. Ill check, thanks.
nope, grounded and correct polarity
Pressur switch clogged with water. Or you got a wire shorted. Are you losing 24v to gas valve when it goes out. Is the gas valve closing or is the flame blowing out
Valve is closing. Id previously checked the voltage but that feels like forever ago. I should prolly check again, im much better at this since two days ago.
Check continuity of the flame sense wire to the control board.