Household thermostats

[Jersey mike]

The reason for this thread is because I’m trying to narrow down a recurring issue with my gas furnace.

Last winter I began having multiple failures.

Some of which are; ignitor not lighting, going out too soon, taking too long to turn on and I’m probably missing another.

Flame sensor; would cut out flame too soon, system would short cycle or fail to run for several cycles.

Other times the furnace would run as it was suppose to for days and weeks on end then poof out of nowhere failures.

This past spring we replaced motherboard thinking that’s the issue.

Why I believe thermostat is involved in some matter is because now the furnace does not like to run properly after more than 2 consecutive cycles. Thermostat will read “73”....call for heat, pre-fan turns on and igniter fails..once, twice or igniter lights and flame turns on and flame sensor shuts it down.

I’ve opened the furnace many times while the failures are going on and whether it’s coincidence I’m not sure but if I tickle the wires leading from the wiring plug for the igniter it will usually light and if there is a flameout a tap or two on the leads to the thermocouple will take care of that.

I’ve been at each lead and tried tightening or lightly squeezing all electric connections but no joy as something is still failing.

There are times when it seems the sensitivity or margin of error of the thermostat have changed. The Thermostat will suddenly shut off the call for heat. I usually have the HOLD set while we’re home and adjust manually during the day. If I adjust thermostat 2 degrees above a setting that failed it will usually fire up no problem but there are times when the recurring igniter or flame sensor are still there.

I have to add, running the A/C all summer was never an issue.

My furnace guy is on vacation until the end of the month so I’m troubleshooting this on the fly but have been doing it since the end of last winter.

System is only 6 yrs old. But it’s not a top of the line system.

First off, your furnace doesn't have a thermo-couple and I highly doubt it's a t-stat problem. From your description of the problem, I'd be looking at the pressure switches. They will cause the furnace not to fire or fire and shut it down when the flue gases meet the inducer fan simulating a flame sensor problem. I have never replaced a flame sensor.....just clean it and put it back in. You could have blockage in the condensate system. Make sure it's draining properly and that the furnace is tilted forward slightly to help it drain. Be a shame to waste dollars on parts you don't need. Let your HVAC guy trouble shoot it when he's back if you not sure   of anything I just suggested. Hard to diagnose from here.  ???  

What Brand is the Furnace?

I forgot it’s not thermocouple anymore, it’s flame sensor.

Brand of furnace (American Standard) is embarrassing to mention because if found (possible rumor maybe) out it’s made from parts that didn’t pass QC of a more well known (Lenox) company.

American Standard......lucky you! 

Probably the most reliable furnace made and no it's not made out of low quality parts. Manufactured by Trane and part for part identical. The Label on the door is the only difference. Be assured, you own a high quality product!

Now, the other thing to check is blockage in the vent system. The venting and condensate are all connected internally and effect whether it will run or not. Lift the intake (combustion air) pipe off the top of the furnace. You'll see within the collar, a baffle full of holes to let the air in but to keep contaminates out like Bee's, leaves and the like. If there is anything laying there, remove it. if there is nothing there, leave the pipe disconnected and run the furnace that way for a few day to see if it operates properly. If it does run properly, there may be something in the pipe or the venting is to long and the pressure switches (two stage) are not liking it. They are designed for only so long of a venting system and the elbows have to be taken into account.

Again I will say, I have never replace a flame sensor. I don't even carry them in my service van. Emery cloth cleans them perfectly! No different than having to clean your battery posts on your car. You don't change the battery because the posts are corroded!

Ok so here’s where I look stupid my unit is ARMSTRONG AIR not American Standard.

I had several tabs open last night researching a few different possibilities on a new replacement.

Diagnostic light usually blinks 3 times during a failure. 3 times on...off...3 times on....off and so on.

[Wizzard]

There in lies the key to your problem,, if you look under the model # of that furnace you will find what that error code means and it will give you a hint what is wrong,
If you give me the model # I will look it up for you.

[Jersey mike]

There in lies the key to your problem,, if you look under the model # of that furnace you will find what that error code means and it will give you a hint what is wrong,
If you give me the model # I will look it up for you.

I tried that last winter and the results were websites selling furnaces, links to online “chats” with “experts” for a fee, HVAC installers in my area and other stuff except for some YouTube videos which I scoured for some answers.



My model # is; A80UH1D090B12-53. Those are Zeros in there not the letter “O”

Serial # 1714M09518

Thanks for going out of your way with this.

[t-man403]

Armstrong is a Lennox with Armstrong labeling.

Anyway, what I said in my last two posts applies to this failure code. There are two hoses connected to the neck or top of the collection manifold that can plug very easily. Check the nipple for the small hose as well there is a filter in the larger hose that can plug. These things AGAIN, are all part of the venting and condensate system and will effect the pressure switch. If there is no blockage you will most likely need to replace the pressure switch.

[Jersey mike]

Armstrong is a Lennox with Armstrong labeling.

Anyway, what I said in my last two posts applies to this failure code. There are two hoses connected to the neck or top of the collection manifold that can plug very easily. Check the nipple for the small hose as well there is a filter in the larger hose that can plug. These things AGAIN, are all part of the venting and condensate system and will effect the pressure switch. If there is no blockage you will most likely need to replace the pressure switch.

Thanks, I’ll look into this tomorrow.

[Jersey mike]

Armstrong is a Lennox with Armstrong labeling.

Anyway, what I said in my last two posts applies to this failure code. There are two hoses connected to the neck or top of the collection manifold that can plug very easily. Check the nipple for the small hose as well there is a filter in the larger hose that can plug. These things AGAIN, are all part of the venting and condensate system and will effect the pressure switch. If there is no blockage you will most likely need to replace the pressure switch.

Thanks, I’ll look into this tomorrow.

I’m looking at my furnace cover off.

Directly in front of me I see the pre-fan attached to the exhaust housing/manifold which leads directly to the chimney.

To the left of the exhaust housing I see the pressure switch with 1 orange colored square tube leading to the lower portion of the exhaust housing. I can blow through the tube into the exhaust manifold without resistance and suck air through it also.

I do not see or appear to have two hoses as you described.

With the hose attached to the pressure switch if I suck air I can hear a click like a closing sound in the pressure switch, if I blow air I get pressure resistance.

I have a new pressure switch on order as well as a new igniter.

[Wizzard]

I had this exact problem. It was some little bit of dirt in the small hose. Cleaned it out and never a problem since

[F6Dave]

I have a new pressure switch on order as well as a new igniter.

The first time my ignitor failed was at night with the temperature well below zero.  Luckily the local hardware store stocked them, so all was well the next morning.

The next failure was caused by a bug landing on it.  As with halogen bulbs, a bit of oil even from your finger will drastically reduce the ignitor's life.  But the hardware store stopped selling them, so I had to drive 40 miles to a plumbing and heating place.

Lesson learned:  I always have a spare ignitor.  That should be a natural for guys who keep spare U-joints and alternators laying around.

[t-man403]

I had this exact problem. It was some little bit of dirt in the small hose. Cleaned it out and never a problem since

And that's exactly what I'm talking about and the Armstrong furnace is famous for it!

Here's a couple pix I took today that may explain the hoses better.

In this picture are the two hoses I was talking about on the vent collar. The one on the left can plug on the inside of the nipple it's connected to. The one on the right goes down to the collection manifold in the next picture.



This is on the bottom right corner and inside at the connection there is a filter. Just squeeze the hose gently and you will feel it. This can get plugged from guys doing a sloppy job cutting the vent pipe to length. Some guys use a resip saw and don't clean out the shavings before cementing the pipe and fitting together. Those shavings end up at that filter.



Anyway, the problem is going to be something stupid when discovered......

[Jersey mike]

I had this exact problem. It was some little bit of dirt in the small hose. Cleaned it out and never a problem since

And that's exactly what I'm talking about and the Armstrong furnace is famous for it!

Here's a couple pix I took today that may explain the hoses better.

In this picture are the two hoses I was talking about on the vent collar. The one on the left can plug on the inside of the nipple it's connected to. The one on the right goes down to the collection manifold in the next picture.



This is on the bottom right corner and inside at the connection there is a filter. Just squeeze the hose gently and you will feel it. This can get plugged from guys doing a sloppy job cutting the vent pipe to length. Some guys use a resip saw and don't clean out the shavings before cementing the pipe and fitting together. Those shavings end up at that filter.



Anyway, the problem is going to be something stupid when discovered......

Thanks for taking the time to post the photos but I don’t have anything that looks like that. No rubber hoses or pvc piping.

My furnace has 2 removable panels, on the bottom is the main blower and circuit board.

On the top section is the gas valve, the pre-fan, the fan housing, the burners. There is 1 galvanized exhaust 3” or 4” leading out the top of the cabinet to the right to my chimney, to the left is the pressure switch. That’s is pretty plain and simple with the exception of some wiring.

No rubber hoses and no pvc piping.

[t-man403]

Ah, so you have a mid-efficient furnace then. I assumed hi-efficient because that is all we have in Canada.
Crap this should be real easy to fix then. When your pressure switch shows up, let us know what happens. I would be putting in one that is a little less sensitive. Also take a look up you chimney to make sure a bird hasn’t died or built a nest in there to cause blockage. Wind can cause failure if you have a lousy rain cap or the chimney isn’t high enough. The problem is intermittent so those are possibilities.

[Jersey mike]

Ah, so you have a mid-efficient furnace then. I assumed hi-efficient because that is all we have in Canada.
Crap this should be real easy to fix then. When your pressure switch shows up, let us know what happens. I would be putting in one that is a little less sensitive. Also take a look up you chimney to make sure a bird hasn’t died or built a nest in there to cause blockage. Wind can cause failure if you have a lousy rain cap or the chimney isn’t high enough. The problem is intermittent so those are possibilities.

I ordered an exact replacement. I got all the numbers off the old part and found it.

What is a less sensitive one?

Mine reads .0.65 PF

Why would a less sensitive one be a good change? Because of my area? Because of my home or the furnace location?

[t-man403]

Ah, so you have a mid-efficient furnace then. I assumed hi-efficient because that is all we have in Canada.
Crap this should be real easy to fix then. When your pressure switch shows up, let us know what happens. I would be putting in one that is a little less sensitive. Also take a look up you chimney to make sure a bird hasn’t died or built a nest in there to cause blockage. Wind can cause failure if you have a lousy rain cap or the chimney isn’t high enough. The problem is intermittent so those are possibilities.

I ordered an exact replacement. I got all the numbers off the old part and found it.

What is a less sensitive one?

Mine reads .0.65 PF

Why would a less sensitive one be a good change? Because of my area? Because of my home or the furnace location?

Altitude or your area, yes.
Not sure what the next one down is for that furnace but stepping down one doesn't create a hazard. May be something like .60 but the one in your furnace now may have a hole in the diaphragm so in doesn't hold vacuum. So the one you just ordered should work fine if that is the case. 

[Jersey mike]

Well new parts came yesterday and today after installing new pressure switch, new igniter and new flame sensor there is no joy in Mudville.

System went back to throwing same code as before. 

We went away for the weekend and system was set to AC because temps were in that zone.

Came home Sunday evening and house was chilly so I tried heat. System fired up like it should and ran fine for 2 times then went back to same issue as before.

[Robert]

Just a thought if you have been through everything and its ok how about the control circuit or computer to run it?

[Wizzard]

Well new parts came yesterday and today after installing new pressure switch, new igniter and new flame sensor there is no joy in Mudville.

System went back to throwing same code as before. 

We went away for the weekend and system was set to AC because temps were in that zone.

Came home Sunday evening and house was chilly so I tried heat. System fired up like it should and ran fine for 2 times then went back to same issue as before.

so did you replace the ignitor or the flame sensor,, they are different. Also you have several limit switches on that furnace. Could be any one of them, but they are easy to check with an ohmeter

[Jersey mike]

Just a thought if you have been through everything and its ok how about the control circuit or computer to run it?

New motherboard was installed last April.

[Jersey mike]

Well new parts came yesterday and today after installing new pressure switch, new igniter and new flame sensor there is no joy in Mudville.

System went back to throwing same code as before. 

We went away for the weekend and system was set to AC because temps were in that zone.

Came home Sunday evening and house was chilly so I tried heat. System fired up like it should and ran fine for 2 times then went back to same issue as before.

so did you replace the ignitor or the flame sensor,, they are different. Also you have several limit switches on that furnace. Could be any one of them, but they are easy to check with an ohmeter

I replaced all 3. The igniter....the flame sensor and the pressure switch.

I don’t know what a limit switch would be.

New motherboard was installed last April.

[Kep]

36 years HVAC tech ...1) should never have to replace a flame sensor , only clean it with emery cloth  2) Ignitor is either good or bad , no in between  3) Never blow through the hose connected to the pressure switch, you will damage the pressure switch.......A) Follow the hose from the pressure switch to where it connects to the furnace , usually at the inducer housing , disconnect it and use a small drill bit or even an allen wrench to clean it out  , these  often get restricted to the point that they will initially allow the furnace to run but then drop out the pressure switch after building a little stack pressure. If this doesn't work , PM me and I will give you my phone number and I can walk you through some troubleshooting.

[Jersey mike]

36 years HVAC tech ...1) should never have to replace a flame sensor , only clean it with emery cloth  2) Ignitor is either good or bad , no in between  3) Never blow through the hose connected to the pressure switch, you will damage the pressure switch.......A) Follow the hose from the pressure switch to where it connects to the furnace , usually at the inducer housing , disconnect it and use a small drill bit or even an allen wrench to clean it out  , these  often get restricted to the point that they will initially allow the furnace to run but then drop out the pressure switch after building a little stack pressure. If this doesn't work , PM me and I will give you my phone number and I can walk you through some troubleshooting.

Thank you for the advice and the offer.

I spoke with the original installer today, he’ll be here in a day or so. He s been away and is taking today to get his calls in order.

He’s been here before, we’ve been battling this issue on and off since about 1 year after installation. The unit will be 6 years old in February. The first time he cleaned the flame sensor and it worked flawlessly for the remainder of that winter and the 2 following winters. At one point he did the clean out of the pressure switch/tube and fan port and again it worked no issue until end of last winter.

 I’m sure it wasn’t his installation but just probable bad unit. I’ve known him for years and has never charged me for any trips here to diagnose the issue. He replaced the motherboard no charge in April when I told him there were now multiple failures beginning to occur.

In March of 2019 we had a crew come in and install a basement French drain system which involved a lot of jackhammering and a super amount of ultra fine concrete dust. While they did tent off the furnace and used high velocity exhaust blowers to remove the dust, some still made its way into the furnace. I vacuumed, used canned air and wiped the furnace to new condition everywhere possible..basically detailed the furnace when they were done but the furnace was running while the me worked, so maybe that fine dust did damage somewhere or accumulated to form a blockage.

[Jess from VA]

Jersey, 25 years ago, I lived through that install of a below foundation french drain around the exterior walls of my basement.  It needed done, but what a huge PITA; having to completely strip my furnished basement, then an industrial project inside your house with jackhammers and dust and mud is no fun.  I finally stapled a shower curtain over the stairwell to keep the crud down there. 

No more water leaking though.  But if I get a power loss in a huge rainfall, it's generator to run the sump or rising water trouble.

I've decided basements are an all around bad idea, unless on Western dry land or very low water table or high elevations.

My region, like most of DC is all swap land everywhere.  The Indians gave it to us for a Capitol and have been laughing about it ever since. 

[Jersey mike]

Jersey, 25 years ago, I lived through that install of a below foundation french drain around the exterior walls of my basement.  It needed done, but what a huge PITA; having to completely strip my furnished basement, then an industrial project inside your house with jackhammers and dust and mud is no fun.  I finally stapled a shower curtain over the stairwell to keep the crud down there. 

No more water leaking though.  But if I get a power loss in a huge rainfall, it's generator to run the sump or rising water trouble.

I've decided basements are an all around bad idea, unless on Western dry land or very low water table or high elevations.

My region, like most of DC is all swap land everywhere.  The Indians gave it to us for a Capitol and have been laughing about it ever since. 

The guys did a great job as far as I know, the system hasn’t been tested yet.

When done they used compressed air to blow down everything, vacuum, sweep and wipe down as much as possible, but there was still fine dust everywhere. I spent days working top down from the floor joists, to walls to floors wiping, vacuuming and mopping and my basement is only partially finished. My next house will have a nice sunroom instead of a basement I think.

If and how that dust may have affected the furnace I don’t know.

The furnace in our shop at work is in one of the dustiest environments there is and fires up every winter and never an issue. It has to be 30 years old and runs like a champ. Hopefully my issue will be resolved soon.

[Jess from VA]

Well, my basement had been finished soon after purchase in 1960, and the guy guy must have spent a whopping $250 total (cheapo crap floor to ceiling).  And it was already stripped.  So with the help of an expert carpenter, we refinished the whole thing (except the unfinished utility room) right after the drain was installed.  Nicest room in the house now.  Sort of my man cave.  

My guys left a cleanout hole in the far corner from the sump hole, so you could stick a hose down there and flush it out.  But I never have.  Once (in 25 years), during a 3 inches of rain in 2 hours event, I got about a cup of water out on the floor when the system just got overloaded.  So I've been pretty happy with the result.

I just got a brand new HVAC AC and furnace this summer.  For weeks now, no AC and only bump the heat on once or twice a day.  Hope you get your furnace sorted, it will be getting nippy soon.

Supposed to get 2 1/2 - 3 inches of rain starting tonight.  

Two solid days of leaf cleanup, and it won't look like I was ever out there after the rain.  Buying a house on a third acre with five 80yo oaks was possibly the stupidest thing I ever did (either that or the 2d wife, I can't decide)   

[scooperhsd]

Try buying a house on 3 1/3 Acres in the middle of a forest, with an inground swimming pool. That was my rock for 20 years.

[Kep]

How did things turn out ?

[Jersey mike]

Service tech came Friday. 2 hours before he came I turned on system on, it fired up on the first try, ran fine until temp on therm was reached and failed each time after that, so I let it continue to fail until he got here.

After watching it and me telling him each way I see and hear it failing, me telling hi of the parts I replaced, him removing duct work to check the air flow from the pre-fan, checking venting to my water heater which shares same chimney, the decision was made to change the gas valve.


Gas valve was changed on Saturday morning and the system has been functioning normally since then.

I’m keeping my fingers crossed for continued warmth.

[Kep]

I've had a few of those lately, intermiitnet gas valve solenoid sticking. You can hear the relay click , but sometimes the solenoid doesn't pull in and open the valve , tap on it and it opens...intermittent problems are a technicians nightmare...if you can't get it to fail when you are there , it's hard to fix.Glad he found it.If you ever have trouble again , feel free to PM me and I'll give you my number.

[Jersey mike]

I've had a few of those lately, intermiitnet gas valve solenoid sticking. You can hear the relay click , but sometimes the solenoid doesn't pull in and open the valve , tap on it and it opens...intermittent problems are a technicians nightmare...if you can't get it to fail when you are there , it's hard to fix.Glad he found it.If you ever have trouble again , feel free to PM me and I'll give you my number.

Were they Honeywell?

Those were his words exactly...”I hate intermittent issues, they’re the worst”

Thanks for the offer also.

I hope this is the end of it.

Big thanks again to everyone for their input, it’s all greatly appreciated.

[Wizzard]

I've had a few of those lately, intermiitnet gas valve solenoid sticking. You can hear the relay click , but sometimes the solenoid doesn't pull in and open the valve , tap on it and it opens...intermittent problems are a technicians nightmare...if you can't get it to fail when you are there , it's hard to fix.Glad he found it.If you ever have trouble again , feel free to PM me and I'll give you my number.

If its a sticking gas valve does the main board still throw a code?

[scooperhsd]

I've had a few of those lately, intermiitnet gas valve solenoid sticking. You can hear the relay click , but sometimes the solenoid doesn't pull in and open the valve , tap on it and it opens...intermittent problems are a technicians nightmare...if you can't get it to fail when you are there , it's hard to fix.Glad he found it.If you ever have trouble again , feel free to PM me and I'll give you my number.

Were they Honeywell?

Those were his words exactly...”I hate intermittent issues, they’re the worst”

Thanks for the offer also.

I hope this is the end of it.

Big thanks again to everyone for their input, it’s all greatly appreciated.

It doesn't matter what is being fixed - (cars, computers , furnaces, etc.) -  intermittent issues, they’re the worst.

[Kep]

I've had a few of those lately, intermiitnet gas valve solenoid sticking. You can hear the relay click , but sometimes the solenoid doesn't pull in and open the valve , tap on it and it opens...intermittent problems are a technicians nightmare...if you can't get it to fail when you are there , it's hard to fix.Glad he found it.If you ever have trouble again , feel free to PM me and I'll give you my number.

If its a sticking gas valve does the main board still throw a code?

Most of the time it will show a ignition failure code or something similar (depending on the manufacturer) because when the valve fails to open and allow gas to flow to the burners, it will not ignite the burners , therefore registering a trouble code . Some manufacturers will allow for a certain amount of "tries" before it locks out and registers a code.

[t-man403]

I've had a few of those lately, intermiitnet gas valve solenoid sticking. You can hear the relay click , but sometimes the solenoid doesn't pull in and open the valve , tap on it and it opens...intermittent problems are a technicians nightmare...if you can't get it to fail when you are there , it's hard to fix.Glad he found it.If you ever have trouble again , feel free to PM me and I'll give you my number.

If its a sticking gas valve does the main board still throw a code?

Most of the time it will show a ignition failure code or something similar (depending on the manufacturer) because when the valve fails to open and allow gas to flow to the burners, it will not ignite the burners , therefore registering a trouble code . Some manufacturers will allow for a certain amount of "tries" before it locks out and registers a code.

The code indicated pressure switch problems and the pressure switch is connected to the gas valve. The codes only give you an indication of where to start looking for the problem. It's hard enough for a "Trained" tech to find the problem at times let alone the home owner so money gets wasted on parts not needed.

Dang I just might have to buy one of those shifter buddys to help out here! 

[Jersey mike]

Luckily I’m only out about $400 in parts and zero in labor.

I have a new motherboard, new igniter, flame sensor, gas valve and pressure switch.

And back to the originality of the thread I still have a brand new thermostat in the box too.