York Furnace problem with pressure switch stuck open

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!

 

Welcome to the forums.

The 4 flash code is failure of the pressure switch to change state or close when the draft inducer starts. It's not stuck it's just not being closed.

Remove the wires from the pressure switch. Hook an ohmmeter on the two terminals. Start the furnace up and a call for heat. The meter should show a change of status of the switch in several seconds. If you don't see a change in meter reading then you need to trouble shoot the pressure switch and related areas.

You removed the rubber hose from the pressure switch and the furnace operated. That is not correct. If the pressure switch does not show a change in status.... the furnace should not start.

Your friend had a manometer..... did he connect it to the hose for the pressure switch ? The little push on fitting at the inducer blower is notorious for clogging.

 

Thanks for the response PJmax. This is actually a 3 flash code(Pressure switch stuck open). I tried the test you suggested and saw the fluctuation. It was open before the call for heat and then closed when called for heat. I did this about 5 times just to make sure. This is a new pressure switch that is only 2 months old.

As for the rubber hose removed from the combustion chamber. This makes sense why it still works as it is just sucking outside air in the basement. Hopefully the attached picture helps.

As for the manometer test. I believe he had it T'd with the existing rubber hoses to make sure we included everything that is on the furnace when running.

It has been acting up all night. Usually it will be okay for a day or two but now it has been worse than ever before.

Any other ideas?

Thanks for your help.

 

I forgot to mention that the push on fitting at the inducer blower was okay. I actually took the whole inducer motor apart a few days ago and couldn't see anything unusual going on with it. All airways clear.

 

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. :NO NO NO:

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.

 

Update.

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. 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.

 

I don't think the winds have anything to do with breaking a pressure switch.

The switch, when closed, should measure very close to 0 ohms. Many ohm meters wont register 0 ohms. Try shorting the leads together. The meter can't read any lower than that reading.

 

I am going through the exact same problems (except for the dead beetles). I had my furnace installed 2008 and within the first year had the service guy out to look at it 5 or 6 times. I had double-checked calculations for exhaust run and though within recommendation I convinced the tech to remove one elbow. It seemed to work for awhile but the pressure problem returned. After a few attempts of the inducer motor cycling without starting the gas and ignition it would start successfully but always seems to be pressure switch error. I am beginning to believe there is a design or internal problem with my unit because problems with my pressure switch fault is random and does not seem consistent for conditions of failing. I had to replace the inducer assy 4 months ago because the veins on the blower blew apart. Has worked great until two days ago and the pressure indicator is back - presently it is not working at all. the inducer starts and runs for about a min then shuts off - over and over... I am considering purchasing a new pressure switch but noticed the recommended part number for my unit (024-27639-001 -- 1.20 PF) has been replaced with Manufacturer Number S1-02435262000. After the research I also noticed my pressure switch is 1.0 PF. I regret buying this furnace because It has always presented problems when least expected and can't afford to replace for a few more years. Please advise?

 

That wouldn't be a pressure switch problem. It will either be a thermostat problem or a control board problem.

You can temporarily add a jumper from the R terminal to the W terminal. If the inducer remains running.... then you have a thermostat problem. If you unit still cycles that would point to a control board problem.

 

Ok I was mistaken on part number for my model and it had the correct pressure switch. I could blow on the burner hose or suck on the inducer hose and the switch would activate the glo plug and then the gas would start. I decided to try a new pressure switch but same problems exist. Next I removed the PVC combustion tube from the inductor motor so I would have no restriction. - same results. I re-installed the combustion PVC pipe. Thinking that since I had to replace the inducer assy 4 months ago because the veins on the blower blew apart (for unknown reason) possibly there was debris that was sucked up through the inducer that caused the veins to blow apart? -- So my thoughts now leads me to think I could have a faulty heat exchanger or condensing coil? I heard there are many reports of secondary heat exchangers de-laminating on other furnaces. In review, if the Inducer is spinning at 3600rpm as it should, and there is a crack or hole in the heat exchanger or condensing coil, then the pressure in the burner chamber would be less than enough to activate the pressure switch properly - Thoughts?

 

Update -- Having started the furnace (with trickery) by having to apply a little pressure to the burner hose and then plugging it I could get the furnace running long enough to heat the house. Then I took out the inducer, disassembled it and inspected it, noticed the squirrel cage was just starting to scrape on the side away from motor (furnace side) and there was about a 1/8 in gap between the wheel and housing on the motor side. So I re-positioned the squirrel cage to the housing just enough to clear and spin freely. Then I applied hi-temp sealer to the housing both halves where they mate together and reassembled, checked wheel again and was free spinning without any rubbing, so I re-installed inducer in the furnace. With everything back in place I replaced the lower cover so the safety switch would engage and the furnace started without any assistance (or trickery) Looks like I am back in the heat zone!