# York Furnace pressure switch stuck open troubleshooting



## divergent (Feb 10, 2014)

Hi,

I am hoping to get some advice on how to fix my York Furnace which is only 6 years old. I have been reading many forums on how to troubleshoot it. It all started back in October of 2013 and am stumped at what it could be. I’ll try to keep this short as possible. 

York Model GY9S060B12UP11K

Back in late October of 2013 I heard the furnace trying to start with the first stage of the inducer motor trying to kick on and then shutting off within about 3 seconds. The error code on the control board was one red blink which indicated per the diagnostics code on the door that it was a controller board fail. I didn't know much about furnaces back then so I just took for granted that it was the control board that was failed and ordered the same exact one from a local HVAC store in town. The weather wasn't unbearable at the time and the furnace would actually work intermittently the next couple days while I waited for the part to get in. Once the new control board came in I installed the new one which was simple as I just took some pictures of how the old one was wired up. Everything started working great again for about 2 weeks. 

After about 2 weeks of installing the new control board it started to do a similar thing except this time the inducer motor would kick on and run for almost a minute and then shut down with no attempt to lite the ignitor. I was getting 3 red blinks now which was pressure switch stuck open. After looking up online at some of other people having the same issue I measured the voltage on both wires going to the pressure switch when the furnace wasn’t running and both were 24V. I ohmed it out and everything tested okay when not running and when I could actually get it to work. This is a two hose pressure switch. One hose to the inducer motor and one to the combustion chamber. I could hear the pressure switch click if I sucked in lightly on the tub that goes to the inducer motor. After troubleshooting a bit more I thought I had it narrowed down to the pressure switch being bad as I could not find anything else being wrong. I ordered the new pressure switch in November and installed it. Everything has been working great since. I thought I had it beat for sure. Now about 2 months later I am back to the 3 blinking lights again stating the pressure switch is stuck open. Back to the drawing board.

I looked up more forums on the internet and checked a few more things. The venting for the furnace on my house is way up high so highly unlikely anything would be in there. I checked both the intake and exhaust PVC pipes with fish tape and found nothing in either of them. 

I had my friend come over with his manometer and check to make sure the inducer motor was running correctly and had the right pressure. Everything looks okay pressure wise.

I took off the water collector near the bottom of the furnace where all of the rubber hoses go and cleaned it out. Nothing unusual and seems to be draining okay when I fill it up with water. 

I also checked the inducer motors nipple where the hose from the pressure switch hooks up and found nothing blocking. 

I then took the hose off the pressure switch that goes to the brass knob going into the combustion chamber(where the ignitor and gas are) and made sure nothing was in the brass knob. For the heck of it I left the hose from the combustion chamber off as I never thought of that being an issue(I have a carbon monoxide detector so no worries). It has run fine for 4 days straight but now back to the 3 red blinks pressure switch stuck open. 

I am at a loss at this point as I have tested everything and can’t figure out why it is doing this every once in a while. The minute I go down and look at it while it is acting up it will start working again so it must be something right in front of me that I am not seeing. I tried moving the wires around while it was acting up but still no luck.

Sorry for the lengthy post but I wanted to make sure I included everything. Any ideas or suggestions would be greatly appreciated. I am no expert at furnaces(only know what I have learned in the last 3 months) but am pretty handy so I can take a look at most things. If pictures are needed as well I can post those.

Thanks!


----------



## beenthere (Oct 11, 2008)

The printed pressure on the pressure switch, is the pressure at which it opens. So what was the differential pressure your friend measured, and what is printed on the switch.


----------



## divergent (Feb 10, 2014)

Hi beenthere,

The pressure switch is labeled as a -1.20 PF. I can't remember the exact reading on the manometer but it was somewhere around 1.5-1.6 reading. 

Thanks.


----------



## beenthere (Oct 11, 2008)

1.5 to 1.6" is barely enough to close it. May have a problem with the heat exchanger, or with the inducer.


----------



## beenthere (Oct 11, 2008)

PS: He did read it as a differential pressure correct? As in he didn't just take the pressure reading from the inducer, right.


----------



## divergent (Feb 10, 2014)

Update. My friend can't get a hold of the manometer anymore since he borrowed it from work last time and can't get one at the moment. I guess last time they raised quite a big deal that one was missing for a day. 

Since the last post the furnace is still getting intermittent pressure switch open fails. I took the PVC pipe off that hooks directly to the inducer. This is about a foot long section that goes into a drain clamp(?) which then hooks on to the main exhaust run going outside. I was poking around in this drain clamp before taking it all apart and a bunch of water came out in a stream. After taking everything apart I found a bunch of dead beetles were stuck in the drain clamp causing the condensation not to flow out one of the drain tubes. Positive that this was the fix I hooked everything back up. Ran great for 24 hours. I kept checking the history on the control board and all was well. Around the second day I went to go check it in the morning and to my surprise the fault code was there again in history(pressure switch stuck open). Looks like it happen at least three times(max history that control board will keep). The minute I catch it doing this I go down an check the one side of the pressure switch(hot side/white wire) and see the 24V. I check the other side(blue wire) and see it as well. I can never catch it when it is not showing 24V on the side with the blue wire. It's almost like whenever I hook up the volt meter it clears the issue for some time. 

No idea what would be causing this. I am leaning towards possibly another bad pressure switch as the inducer motor sounds fine and I see no blockages in any of the drain hoses or anything in the intake or exhause PVCs. I am thinking of buying my own manometer but confused on which one to by. I would need the T's and tubing as well which I don't think come with them. Any recommendations on a manometer under $100 and where I can buy extra tubing and T's so I can test the pressure on this again. 

Any other ideas on what would be causing this intermittent issue. The house stays heated so not a critical issue but quite annoying that it is doing this considering this is only a 6 year old furnace in a 6 year old house.

Thanks.


----------



## beenthere (Oct 11, 2008)

Not sure they make a dual port for less then 160.


----------



## Bigt23 (Feb 8, 2014)

What size is the exhaust pipe going outside 2 or 3 inches? How many btus is the furnace?


----------



## Bigt23 (Feb 8, 2014)

Looks by the model it is 60000 btus. The reason I ask is this. That particular furnace vented with 2 inch pipe has a maximum distance of 60 feet. Each elbow you put in you lose 5 feet . 2 45s count as an elblow. So max of 60 feet let's say you have 4 elbows. Now your only allowed 40 feet and so on. If you move up to 3 inch pipe your allowed a max of 85 feet for that furnace w the same deduction for each elbow... too many elbows, too long of a run, or an undersized pipe will also cause this problem. .

Now I know your thinking it's been fine for 6 years why now? If the piping was sized and was operating at the bare minimum over time the inducer loses efficiency and will not perform like it used to. U may see it working and it may sound OK but if the venting is undersized it may have lost just enough to make a difference. Also your venting develops air pockets over time which could attribute to the sudden issue. Or it could just be that your inducer just lost a bunch of efficiency and the piping could be ok. 1.5 to 1.6 is not enough and on a really cold day it could drop below 1.2 keeping your pressure switch open. Had this identical problem with a customer last month. Changed the inducer and fixed the issue but the real problem is an undersized vent pipe. His problem will eventually return once the inducer loses some power over the years


----------



## divergent (Feb 10, 2014)

Thanks for the response aa7483!

Sorry I did not see your reply's until now. Usually I get email notifications but didn't see any. 

The exhaust and intake piping is 2". There are 4 elbows on the exhaust and 3 on the intake. From furnace to outside both are about 25'. So if I add on the elbows per the calculations you provided.

25'+20'(4 elbows)=45' exhaust
25'+15(3 elbows)=40' intake

I can't be for certain on the manometer readings as I wasn't really paying attention and those numbers are all i can remember. I would have to get another manometer from somewhere to really check the pressure again.

Here is an update as of today...

So it is really windy outside today and my furnace is having a heck of a time with the pressure switch being stuck open. I can hear the wind being pushed down the exhaust and intake vents that go outside to the side of my house. The strange thing is when I tested the pressure switch resistance by sucking in on the hose that connects to it. I put my multimeter on the pressure switch and suck in on the hose but it is not ohming to 0. I had the tone on and didn't hear anything. I know my multimeter is working because if I touch the two leads together it makes a tone and I read 0 ohms. I could have sworn I have checked this before by sucking in on the pressure switch hose and it read 0 ohms. I would think any switch would work this way. Open and closed. I can see it bouncing around on the mulitmeter in ohms but never getting to 0. Does this sound like yet another bad pressure switch? Could the winds outside be somehow breaking the pressure switches? Thanks.


----------



## yuri (Nov 29, 2008)

the wind can trip the press switch especially if the installer did not terminate the pipes properly. post a pic of them, normally the intake has a 90 deg elbow pointed down so the wind does not blow in it and cause a problem. if you have the install manual look at it and it will tell what York wants. Our man Beenthere is a York guy and if you post a pic later he may help.


----------



## divergent (Feb 10, 2014)

Here are some pics of the inside and outside. There is about 15' more PVC pipe in the picture(first picture) with the furnace that goes straight to the outside of my house(second picture). Thanks for everyone's help on this so far. Really appreciate your time and patience.


----------



## divergent (Feb 10, 2014)

As for the pressure switch. I needed to get the furnace back up and running since it is only 20 degrees out here today. The pressure switch was not closing at all. Even if I would lightly suck on the hose that goes to the inducer blower. I took it out and gave it a few good taps on the cement basement floor(probably not the best I know) and now it ohms out to 0 when I suck in and everything is up and working. Strange that the pressure switch would be getting in some stuck mode even though I could hear it opening and closing. If there is wind blowing in and out of the intake and exhaust though when the furnace is off I guess there is a chance there is enough air to constantly toggle the pressure switch and even possible to break the diaphragm inside? Just guessing at this point. I never thought of this as a wind issue but I have always had winds behind my house for some reason even on calm days. Thanks.


----------



## yuri (Nov 29, 2008)

You CANNOT keep sucking on that pressure switch as it has a delicate diaphragm and is now damaged and should be replaced for safety reasons. Unfortunately people read that on the net and get carried away with it. If the intake is turned down outside then the other pipe is exhaust and you should see steam coming out. It may be better if the exhaust pipe has a T on the end of it so the wind does not blow straight into it. the tee goes on with one end open vertically to let the smoke out and the other open down so water can fall out. I would get one and a 6" piece of PVC pipe and stick it on w/o gluing to test it and see if it works. Glue it on later. Sometimes we have to adapt to the wind etc and that may not be in the manual but it is very common practice with Carriers and other brands.


----------



## Bigt23 (Feb 8, 2014)

Your terminations look ok to me. If I were a betting man I would say the problem is your inducer . It's probably weak and the wind is probably causing an intermittent pressure switch failure because of it. Gotta get a manometer on there to be certain though


----------



## divergent (Feb 10, 2014)

Thanks for the responses guys. I have two pressure switches at the moment. The original and the replacement. I have the replacement one back on right now after I had tapped it on the cement floor a few times. I know it probably doesn't matter but I was sucking on the hose very lightly. Not at full strength. Just seems odd that it wouldn't close at all per the ohm test and now it closes okay after tapping it on the cement floor. 

As for the extra PVC pipe outside. So stick a 6" straight off the exhaust pipe and then put the T on pointed up and down? 

Any suggestions on a manometer I could order online? I need to get one that comes with T's and tubes so i can test it properly. 

Thanks again for everyone's help.


----------



## Bigt23 (Feb 8, 2014)

That's good advice on yuris part. It doesn't matter if your doing it lightly or not. Those diagrams are meant to operate as stated and aren't designed to withstand much more than there rating. Your putting an uncontrolled and undetermined load on it.


----------



## Bigt23 (Feb 8, 2014)

I use this. Works well. http://www.amazon.com/gp/aw/d/B000OUV2D0


----------



## yuri (Nov 29, 2008)

I would put the tee on and order a new pressure switch. Yours has 2 ports on it so you need a 2 port differential pressure manometer which is more expensive. Try what I said and you can save some $$ on a manometer.


----------



## divergent (Feb 10, 2014)

Thanks aa7483. Would this one work with my type of pressure switch that has two hoses? Or would I just hook up this manometer straight to the inducer motor to see what its pressure draw is and go from there? 

The pressure switch is rated -1.20 PF and has one hose going to the inducer motor and one to the combustion chamber(see earlier post). 

Thanks.


----------



## yuri (Nov 29, 2008)

I looked up mine, a UEI em 201


----------



## divergent (Feb 10, 2014)

Thanks yuri. I will give the T a shot. Should I put a 6inch piece on the exhaust first and then put the T pipe on? Thanks!


----------



## yuri (Nov 29, 2008)

you need a 6" piece of pipe to go in your exhaust elbow and stick into the side of the T. imagine this T turned 1/4 turn clockwise. google that manometer if you want and Amazon has some. also make sure the condensate is draining from the furnace properly and the drain line is not kinked. the condensate trap may need to be flushed with warm water and bleach also. if the condensate does not drain fast enough then it can backup in the secondary heat exchanger and cause press switch tripping problems.


----------



## divergent (Feb 10, 2014)

Yuri,

I found these two pressure switches on amazon

http://www.amazon.com/UEi-EM201-Dif...TF8&qid=1393007950&sr=8-1&keywords=UEI+em+201

http://www.amazon.com/UEi-EM201B-In...TF8&qid=1393007950&sr=8-2&keywords=UEI+em+201

Where did you get your T's from and tubing for this meter?

I am not going this route at the moment but just want to have it in case I need to go this route. 

Thanks.


----------



## yuri (Nov 29, 2008)

the manometer is expensive but built like a tank and heavy duty so Pros use it. the tee and pipe I would try get from a local HVAC shop or pexsupply.com but the pipe comes in 8 foot lengths. HDepot may have white pvc and the tee from pexsupply or HDepot. the tubing you can get from a autoparts store, vacuum line tubing. all you do is pull off the tubing from the switch and hook it up to the manometer and start the furnace and it will run for 30 seconds before locking out. you can get plastic tees from the auto parts store for vacuum tubing and tee it in if you want to watch it while running but that may not be necessary just to see the vacuum at startup.


----------



## divergent (Feb 10, 2014)

Thanks again yuri. I will see if the local hardware store has some short 2" PVC and the Tee. 

One more question. Should the pressure switch be mounted vertically or horizontally? Does it make any difference? Currently mine is mounted vertically which is how it was during original install(see first pictures). 

Thanks.


----------



## divergent (Feb 10, 2014)

I can't get out to the store until tonight or tomorrow. Just for the heck of it I wanted to see which pipe all the wind was coming in since I could hear it very well right by the furnace. I assumed it was coming in the exhaust since that one is pointed out(see previous pictures). I taped the exhaust closed temporarily and went back inside. To my surprise I still heard the wind coming in. I tapped off the intake which is pointed down and then wind noises stopped. Not sure how the wind is going UP the intake pipe. Should I still continue with the T on the exhaust pipe? Would the wind coming in the intake cause any issues? Thanks.


----------



## Bigt23 (Feb 8, 2014)

Wind coming in the intake could cause some turbulence in the flames but a back draft in the exhaust would cause the issue your having.


----------



## yuri (Nov 29, 2008)

Yeah, wind coming in is not a problem but the ventor having to work extra hard against the exhaust can cause your problem. Sound transmits thru those pipes so that is not a great way to diagnose problems.


----------



## divergent (Feb 10, 2014)

Alright. So I put on the extra 6inch PVC and T on the exhaust(see picture). Seems to be working so far. Although, the furnace has been working most of the day ever since I tapped the pressure switch on the cement floor. Winds have been the same since last night. Will give this a shot for a few days to see if it changes anything. This has run for almost 5 days straight sometimes with no issues and then it will act up again. Today was the first day that the pressure switch was refusing to close no matter what I did(except tap it on the floor)Will hopefully update with good news. Thanks for everyone's help!


----------



## yuri (Nov 29, 2008)

Get a new pressure switch soon as it is actually a safety device. If it is inaccurate then the burner may not get enough air and become dangerous. The switch proves enough air and draft for safe combustion and needs to be accurate and reliable.


----------



## divergent (Feb 10, 2014)

New pressure switch has been ordered. Should be here by late next week. When I reinstall it should I mount it vertical(originally how it was) or horizontal? Does it matter? Thanks.


----------



## yuri (Nov 29, 2008)

put it the way you found it vertical.


----------



## divergent (Feb 10, 2014)

Woke up last night to the furnace acting up again(it is almost like an alarm clock to me at this point) with the pressure switch stuck open. Took Voltage readings on the pressure switch while the inducer was on. Checked on the side I know should always have 24V was good. Checked the other side and there was nothing. Gave the pressure switch a few good firm taps with a screw driver and presto it works again. I also ordered a manometer(same one that yuri has) to help troubleshoot this further since the only way to really figure this out is to know what the pressure draw is and if it is too low. Manometer should be here on Tuesday hopefully. May need some help setting it up but will give it a shot first. Stay tuned. I do know for sure that this furnace does not want me to get a good nights sleep as it seems to only act up in the middle of the night.


----------



## Bigt23 (Feb 8, 2014)

Generally the colder it gets the lower your vacuum pressure will be which could explain having more issues at night. I think your going to wind up finding your draft inducer as the culprit.


----------



## yuri (Nov 29, 2008)

Yeah, the cold air is denser which slows down the ventor fan. Still cheaper to buy a manometer than pay someone to do it.:yes:


----------



## divergent (Feb 10, 2014)

Received UEI EM201B manometer this afternoon!:thumbsup: Furnace has been acting up at night only for the last few days. After a few good firm taps with a screw driver against the pressure switch everything will work until the next night. 

So I hooked up the hose that goes to the inducer up to the + port of the manometer and hooked up the hose that goes to the combustion chamber to the - port of the manometer. Zeroed out the manometer and put it on In-WG(Inches water gauge) for the scale.

Turned furnace on and the manometer is reading -1.85(fluctuating to -1.84, -1.86 at times). I did this three separate times and all three times were the same.

The pressure switch is rated -1.20 PF. So this should be plenty to close it correct? Is there any other tests I should try at the moment? Only thing I can think of at the moment is to check the pressure throughout the day as it gets closer to night to see if it is dropping. I am not sure what this inducer is rated for but I would think that all depends on your intake and exhaust run as well.

Thanks.


----------



## Bigt23 (Feb 8, 2014)

Looks to me like your inducer is weak. You should see more than that . And on a colder day when it's windy it may be getting down low enough to knock the pressure switch out. If you want to ensure your venting system is not the culprit disconnect the vent pipe and start the inducer. Disconnect the pressure switch first so the flames don't ignite. Take a reading with the pipe out. If it's astronomically higher there is a problem with venting. If only marginally higher it's your inducer.


----------



## beenthere (Oct 11, 2008)

That should be enough to close it.


----------



## Bigt23 (Feb 8, 2014)

Should be enough but on a windy day or on a cold night it may be dropping too low intermittently. Usually like to see it above 2. I was working on one a few months ago started out 1.8 to 1.9. After running for a while it dropped below the 1.20 mark .


----------



## divergent (Feb 10, 2014)

I forgot to take off the PVC T on the outside exhaust before I took the manometer measurements. I took off the T and now the manometer reads about -1.94(In-WG). I did get the new pressure switch today as well and have installed that to make sure it works okay. I am going to hold off on taking the inducer off as it is such a pain because of where the bolts are. I will check the pressure readings later tonight and before I go to bed to see if anything changes. In a way I am hoping to see something change with the pressure but in another way I am not as I don't feel like spending even more money on an inducer motor. 

Will keep you all updated.

As always i appreciate everyone's help.


----------



## yuri (Nov 29, 2008)

Set your alarm clock and do a test at night is the only way 2 know. That is enough to close the switch easily.


----------



## divergent (Feb 10, 2014)

Update.

I checked the manometer readings again after my last post and it read -1.8 again. I must have forgotten to zero out the manometer when I had read the -1.94 before. 

I checked it again a couple times at night once at 9pm and once at 10pm. Both readings were -1.77 to -1.8. 

Checked it again at 4am and still at the -1.77 and -1.8. 

Checked it again this morning at 7am and same readings -1.77 to -1.8

At this point all I can really do is wait and see if it happens again and then put the manometer on it if it does happen to see if the pressure is changing.

Any other suggestions before I reset the history on the control board and let it run for a few days?

Thanks!


----------



## yuri (Nov 29, 2008)

remove and flush the condensate trap with warm water and bleach. if it is not draining fast enough then it will back up water into the secondary heat exchanger and trip the switch.


----------



## divergent (Feb 10, 2014)

Cleaned out condensation trap again with warm water and bleach. I also did this a few weeks ago and didn't see anything unusually. Some small specs of crud or dirt but nothing big. So far the furnace has been running good with no issues since the pressure switch has been changed out. Unless there are some other suggestions I will continue to just monitor it. Thanks again for everyone's help so far!


----------



## divergent (Feb 10, 2014)

Still running good since last post. :thumbsup: Has been two days straight now with no issues. Hoping it stays. Fingers are crossed. No idea how the replacement pressure switch would have gone bad in two months. Will update in a few more days and then call it good at that point. Thanks again for everyone's help!


----------



## divergent (Feb 10, 2014)

Furnace still running good. :thumbsup: History still clear. Must have been another bad pressure switch. Thank you beenthere, aa7483, and yuri for all of your help. I now have a great tool to use later on when testing furnaces and feel even more comfortable troubleshooting furnaces. Hopefully I am not back on here anytime soon.  Hope others can learn from this post. Thanks again!


----------



## yuri (Nov 29, 2008)

Glad to hear it is working. Pressure switches are all cheaply made offshore these days and you get duds. Years ago they lasted for 20 yrs or longer but they don't make that quality anymore in appliances or anything.


----------

