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divergent 02-09-2014 09:52 PM

York Furnace pressure switch stuck open troubleshooting
 
1 Attachment(s)
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. Iíll 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 wasnít 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 canít 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 02-09-2014 10:12 PM

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 02-09-2014 10:41 PM

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 02-09-2014 10:45 PM

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

beenthere 02-09-2014 10:46 PM

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 02-14-2014 07:02 PM

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 02-14-2014 11:59 PM

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

aa7483 02-18-2014 12:46 PM

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

aa7483 02-18-2014 03:21 PM

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 02-21-2014 11:03 AM

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 02-21-2014 11:17 AM

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 02-21-2014 11:38 AM

2 Attachment(s)
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 02-21-2014 11:51 AM

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 02-21-2014 12:46 PM

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.

aa7483 02-21-2014 12:48 PM

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


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