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View Full Version : Intertherm gas furnace won't start.



Ceci Horodyski
10-03-2011, 01:22 PM
Help, please. I think it is a mid efficiency one. Per diagnostic code, "pressure switch stuck on close". Have done quite a bit of trouble shooting, but not getting anywhere. Now nothing happens at all when I turn the thermostat to heat. When this first started a few days ago, I very gently blew through the rubber hose that connects to the pressure switch and for good measure gently blew through the other end of it where it connects to a metal nipple on the surface of the furnace "body". It actually did start up and I had to lower the temp. since it was getting too hot. I as all happy, but then the next morning noticed no heat again so was no longer all happy. It did again turn on by "itself" the following day, but nothing since then. Yesterday, removed the pressure switch and noticed some water came out of it(during the summer the humidifier backed up and the water was probably from that). I shook it out and let it dry out for half a day and put it back into the furnace. Still same code showing. I took the switch off again and blew through the plastic nipple and can hear the diaphragm move and had it checked at a local parts store and they did a meter reading or something and said it is working. I then turned off the furnace again and removed the wire that goes into the pressure switch and put the power back on, bypassed the power off since the furnace door was open(only did it for a few seconds since not good to be bypassing the pressure switch) and the draft inducer did kick in(saw the fan that is visible spin very robustly and heard it so assume that the draft inducer is working). I haven't checked the flue yet since it seems like it is not going to be easy to disconnect that and not sure if any not good gases will be left in there(I would think not since it hasn't been used much). Is that correct? The only other thing I can think of is that the circuit board is somehow not good or there is some kind of "lock down" that needs to be reset since it seems the problem has to be somewhere in the beginning of this whole heating cycle since if it were later on, there would be some other diagnostic code and think this pressure switch code would show up at the beginning of the heat cycle(pressure switch usually on open, furnace "senses" that, which lets the draft inducer do its thing, which then closes the pressure switch, and then the rest of the sequence as far as I understand things, but maybe I am not understanding correctly). Well, that is about it, I think. Oh no, I did forget something. When I turn the thermostat fan to "on", the fan does run. Not sure what that tells me, but it seems relevant to me. Hope someone can enlighten me since not a good time financially to be buying a new furnace(would end up having to do that since it is 14 years old and I know how much just those service calls are and how much having a part replaced is if not done by one's self and already put a fair amount of money into this furnace/air unit part already, but really think there is a relatively simple fix that I can do myself or maybe I am wrong). Helpppppppppp, pleassssssssseeeeeeeeeee.

Thanks,
Ceci

Steven Turetsky
10-03-2011, 01:36 PM
Call the manufactuer. ask for technical assistance.

Harry Janssen
10-03-2011, 02:10 PM
I hope you are a furnace technician,or that you are only trying to fix your own furnace
If not,and you are trying to help a client,guess what,when the repair man calls,he will blame all the issues on you,since you tried to repair it

Ceci Horodyski
10-03-2011, 02:13 PM
I thought of that, but couldn't find a number, but decided to try again and actually this time found a number and called. Like I thought, was told they don't have tech support for home owners and to call a dealer and they would come and as I said, not ready yet to do that for sure since I don't think it is some super big part that needs replacing.

Thanks,
Ceci

Ceci Horodyski
10-03-2011, 03:24 PM
Oh, think you are a bit confused since your first comment is wayyyyyyyyy off base(service tech.). If I were a service technician would hope I would have it fixed by now. Oops, forgot, many wouldn't until they threw every part into it they could think of. Anyway, no service tech is going to blame me for anything since first of all, it's my own darn furnace, obviously and if I don't figure this out myself with helpful comments from others(turning power source off at appropriate times obviously, no more over riding any safety switches, not even for those few measly seconds which I did) will be getting a new furnace, dear. If you have any helpful comments, Harry, would be glad to read them otherwise gracias, bye.

Ceci

wayne soper
10-03-2011, 03:30 PM
try a blow dryer on the removed switch to dry it out

Stuart Brooks
10-03-2011, 03:33 PM
Sounds like the the control valve is bad and the diagnostic is telling you there is no gas flow because the gas control valve is stuck in the closed position. Therefore, no gas pressure. Could be trash in the gas line blocking the valve. This will sound like a stupid question but have you checked to see if the gas supply valve is in the open position? How about the meter shutoff valve?

Ceci Horodyski
10-03-2011, 03:48 PM
Wayne,

So, you don't think the pressure switch has dried out enough? I thought when I blew through the nipple and heard the diaphragm move that it was telling me it was in proper working order and when they tested it with that meter and it came out ok it was telling me it was in proper working order. Am I wrong? Hey, getting some replies finally to my post. Good. More heads better than one head, mine.

Thanks,
Ceci

James Duffin
10-03-2011, 03:49 PM
The purpose of the pressure switch is to prove that the draft inducer is actually running before the gas valve can open. If the pressure switch is already made when it is time for the draft inducer to run you get the error code you mentioned. It sounds like you have a bad pressure switch. I suggest you confirm that with a licensed HVAC contractor.

Ceci Horodyski
10-03-2011, 03:51 PM
I don't understand why you would think it may be a gas control valve problem. Please explain. The diagnostic is saying that the "pressure switch is stuck on close" so how does that tell one that it is a gas control valve problem?

Thanks,
Ceci

Ceci Horodyski
10-03-2011, 03:54 PM
James, I think it may also be that because it got wet, but what I don't understand is why does the diaphragm moves when I blow/suck through the plastic nipple of the switch and why the meter read ok when they took the reading of the pressure switch at that parts place. Please explain if you can.

Thanks,
Ceci

Stuart Brooks
10-03-2011, 04:03 PM
James, I think it may also be that because it got wet, but what I don't understand is why does the diaphragm moves when I blow/suck through the plastic nipple of the switch and why the meter read ok when they took the reading of the pressure switch at that parts place. Please explain if you can.

Thanks,
Ceci

Things fail. That's part of being a home owner. Could be a bad wire connection, a bad control board or more than one bad sensor. Humidifier backed up? Why was it on in the cooling season? Central humidifiers often cause more trouble than they are worth.

Ceci Horodyski
10-03-2011, 04:17 PM
Stuart, how did you copy my last post onto your post? It drives up the wall that I can't see what I am replying to since my brain is a bit old so can't remember things as well as when it was young. :)

Thanks,
Ceci

Ceci Horodyski
10-03-2011, 04:22 PM
I don't think the humidfier was on, but the AC was on and the water from it wasn't draining properly from what I understand from the PVC pipe that was coming out of the humidfier(I think that is what it is since it has a wire coming from a "humidfier" control to it). Somewhare along where it entered the humidfier, the piping was clogged up so there was no place for the water to go except down into my lovely furnace parts. I agree with you, they just cause trouble since not the first time it's happened. Think it is the third time it's happened. Next one, getting rid of that part. So, what does one do during the winter when the air gets super dry from the heat?

Thanks,
Ceci

Ceci Horodyski
10-03-2011, 04:29 PM
Things fail. That's part of being a home owner. Could be a bad wire connection, a bad control board or more than one bad sensor. Humidifier backed up? Why was it on in the cooling season? Central humidifiers often cause more trouble than they are worth.

At least I figured out how to reply with your quote pasted on. HaHa.
OK, don't think it is a bad wire connection since everything seems on tight, super tight. What makes you think it could be a bad control board? Bad sensor, possible, since still think that pressure switch is suspect, but don't understand why the diaphragm moves if I blow/suck through it and when it got tested it tested out ok. Isn't there a way to "unlock" the diagnostic to start over?

Thanks,
Ceci

James Duffin
10-03-2011, 04:36 PM
James, I think it may also be that because it got wet, but what I don't understand is why does the diaphragm moves when I blow/suck through the plastic nipple of the switch and why the meter read ok when they took the reading of the pressure switch at that parts place. Please explain if you can.

Thanks,
Ceci

The diaphragm in the pressure switch is deigned to operate at a very low pressure (if I remember correctly it is about 2" wc). When you blow into it you are blowing hard enough to make even a bad switch make and break the contacts. The switch is important because if the draft inducer fan is not running and the burners light the furnace will not vent the fumes properly.

Ceci Horodyski
10-03-2011, 05:52 PM
The diaphragm in the pressure switch is deigned to operate at a very low pressure (if I remember correctly it is about 2" wc). When you blow into it you are blowing hard enough to make even a bad switch make and break the contacts. The switch is important because if the draft inducer fan is not running and the burners light the furnace will not vent the fumes properly.


Thanks, James, please keep "talking". I think I read that before somewhere else on the internet, but can you explain what that meter reading of the pressure switch that was done at the parts shop tells me. Supposedly the reading was ok. From what I saw and understand, external pressure was put into the pressure switch and the reading told the guy that it was operating oppropriately(the guy looked at some label on the switch which told him at what pressure, I think, it should be within). Darn, should have asked more questions when I was there, but the younger guy doing it was friendly, but the other guy directing him wasn't so much on the friendly side. So, guess I am asking you if it is possible for that reading to be ok, but the actual switch to still not be ok? If yes, why? I'm sorry for asking so detailed questions, but trying to understand things which I really never wanted to understand, but have no choice in a way. I can help you pick out a nice purse for your wife/significant other since am very good at understanding such things. Yes, picking out just the right purse is much more complicated than you would realize. :)

Thanks,
Ceci

Ceci Horodyski
10-03-2011, 06:04 PM
The diaphragm in the pressure switch is deigned to operate at a very low pressure (if I remember correctly it is about 2" wc). When you blow into it you are blowing hard enough to make even a bad switch make and break the contacts. The switch is important because if the draft inducer fan is not running and the burners light the furnace will not vent the fumes properly.

Yes, I understand that thing about the draft inducer finally. Was just havng a hard time understanding the sequence since most sites on the internet leave out that the switch first needs to be proven in the right place, then the draft inducer kicks in. Most sites start out with the draft inducer, then go into the pressure switch discussion.

So, when I saw the fan turning in the draft inducer, is that the whole thing or is there a wheel inside that I can't see that also turns? I think there is, but just making sure. It would be good if the problem is the pressure switch since that draft inducer is much pricier.

Thanks,
Ceci

James Duffin
10-03-2011, 06:15 PM
The important thing is that the switch works consistently. Here is a video that may give you some troubleshooting ideas. You can cut the gas off to the unit and run it to check the operation of the pressure switch in real-life operation. If the switch reads zero ohms with the unit off then it is bad.


Checking the pressure switch on a gas furnace - YouTube (http://www.youtube.com/watch?v=P3-Ki-eEWo8)

Ceci Horodyski
10-03-2011, 06:32 PM
The important thing is that the switch works consistently. Here is a video that may give you some troubleshooting ideas. You can cut the gas off to the unit and run it to check the operation of the pressure switch in real-life operation. If the switch reads zero ohms with the unit off then it is bad.


Checking the pressure switch on a gas furnace - YouTube (http://www.youtube.com/watch?v=P3-Ki-eEWo8)

Oh, that is funny, watched the same YouTube video. It's a good video. If I remember correctly, have watched a bunch of them, the guy has a series of them which are all good. Please clarify something. You say "in real-life operation", but then say "if the switch reads zero ohms with the unit off then it is bad". So, is the unit running or off? Don't forget I'll steer you to just the right purse.

Thanks,
Ceci

Harry Janssen
10-03-2011, 06:43 PM
No were in your post did you state it was your own furnace,and thanks for your smart ass comments,I love you to.

Ceci Horodyski
10-03-2011, 07:07 PM
No were in your post did you state it was your own furnace,and thanks for your smart ass comments,I love you to.


Oh come on, get real here. I posted a whole life story about the funace. Only thing I left out was if it had heart burn or something. So, do you have any helpful comments or not? Would appreciate it if you did. Love you too.

Thanks,
Ceci

Ceci Horodyski
10-03-2011, 07:31 PM
No were in your post did you state it was your own furnace,and thanks for your smart ass comments,I love you to.

Another thing, Harry from Canada, I also did say I would have to buy a new furnace since it's 14 years old so what does that mean to you? Do you think I just go about buying new furnaces for others. Anyway, still waiting for that helpful comment of yours that you need to provide in order to make it up to me since you were kind of mean in your first comment to me. Yes, Harry from Canada, you were.

Ceci

Ceci Horodyski
10-03-2011, 07:56 PM
The important thing is that the switch works consistently. Here is a video that may give you some troubleshooting ideas. You can cut the gas off to the unit and run it to check the operation of the pressure switch in real-life operation. If the switch reads zero ohms with the unit off then it is bad.


Checking the pressure switch on a gas furnace - YouTube (http://www.youtube.com/watch?v=P3-Ki-eEWo8)

So, James, is the following item what I would have to purchase to do that test? I think it is. I would have to order it through Home Depot since they don't carry it. Do you know what kind of shop I should call to see if they carry such a thing since rather not wait for it? Or maybe I should just buy a new pressure switch(good possibility that is the culprit of me freezing my tootsies off) since that meter reader or whatever it's called cost as much as a new pressure switch, I think. I don't think I will be needing it for a longggggggggg time again so not sure I want to actually have one and then when I need it again won't probably be able to find it anyway. Now, if it were a purse or something like that, I could see it as a worthwhile investment. Yes, woman are from Venus, men are from Mars kind of thing.

Professional Digital Multi-Meter-RP4020 at The Home Depot (http://www.homedepot.com/h_d1/N-5yc1v/R-100671269/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053)

Ceci Horodyski
10-04-2011, 08:37 AM
The important thing is that the switch works consistently. Here is a video that may give you some troubleshooting ideas. You can cut the gas off to the unit and run it to check the operation of the pressure switch in real-life operation. If the switch reads zero ohms with the unit off then it is bad.


Checking the pressure switch on a gas furnace - YouTube (http://www.youtube.com/watch?v=P3-Ki-eEWo8)

James, I decided to just go buy the pressure switch since don't like messing with anything that has the word "ohm" in it. Kind of scares me. And like I said, didn't make sense to me to go buy an ohmmeter and like you said, the important thing is that the pressure switch needs to work consistently and in real life(connected to the furnace). Also started thinking when that guy tested the switch, it was down on the table so maybe that influences the test results somehow. Anyway, good news. It was the pressure switch so now have glorias heat and didn't have to buy a new furnace to get that glorias heat. When I first put the new pressure switch forgot to reconnect the tube and then got a diagnostic code of "switch stuck on open" instead of that old code of "switch stuck on close" so got disgusted and turned off the furnace since didn't want something not good to happen, wouldn't have happened anyway since the smart ass furnace wouldn't have let it happen, but didn't give up so opened the furnace againnnnnnnn and saw that I had forgotten to reconnect the tube.

James, I especially want to thank you very much for your input since that kind of helped me confirm I was on the right track since everything seemed to be pointing to that darn pressure switch even if supposedly was working properly. Also, want to thank everyone else who tried to help. It was very nice of you guys.

Harry from Canada, don't you be thinking I shouldn't be messing with the furnace since I was never, ever going to go any further than the pressure switch since I know my limits very well, but had a good idea that the problem was at the beginning of the heat cycle and from this whole experience have learned that those issues aren't that complicated. Hope you have a good winter with plenty of heat, Harry from Canada.

Thanks,
Ceci

Garry Sorrells
10-05-2011, 04:53 AM
Ceci,

You can find inexpensive meters. Since you seem like a DIY person you really need to have one.

You probably wasted more time futtzing around in the dark, add to that the cost of fuel to go to the parts place to have something tested rather than a little investment into a tool that actually could tell you something.

Ceci Horodyski
10-05-2011, 08:34 AM
Ceci,

You can find inexpensive meters. Since you seem like a DIY person you really need to have one.

You probably wasted more time futtzing around in the dark, add to that the cost of fuel to go to the parts place to have something tested rather than a little investment into a tool that actually could tell you something.

Hey, thanks Garry, but I am not a DIY at all so that is why I futtzed around on the internet/in the dark so much to try to figure this out since don't like to touch furnaces or anything with the word "ohm" in it. The parts store is right across the street from my house, lucky me, so no real time wasted there.

Ceci