# Pressure switch stuck open? 2 areas im looking @



## biggles

if the motor is hot to the touch it might be locked up with power going to it...seems the pressure switch is doing its job not bringing on the gas.with power up and meter on the 2 wires on the switch if it is open you will get a reading,if closed you get no reading except each terminal to ground.shut the furnace and try to free spin the IDM squirrel cage CW?CCW might break it loose.to quick check the circuit for the burner do a jump on the pressure switch with a short jumper for 2 seconds you should heae the spark kick in this proves the switch is waiting on the air pressure from that locked up IDM.Caution ......you can't run the furnace without the IDM running


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## dac122

First verify your inducer is running. Its usually the first thing in the ignition sequence. If 90+ AFUE furnace go check the exhaust pipe for an obvious draft coming off. If < 90+ AFUE (ie in the 80) remove the exhaust duct and verify draft. If she's not spinning, remove the inducer and see if it will free wheel. The inducer could be jammed, blocked, have dead spot on motor, etc. The inducer must spin or else nothing works.


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## 1001miles

k so i tested the inducer while it was humming (while furnace was trying to begin startup process. 

White to ground .6 amps

Black to ground 120 amps.

So I believe the fan is the culprit. Are you sometimes able to clean/lube it? 

Hate to ask but what is ccw?


Thanks for all the insight guy/gals!


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## DangerMouse

that would be volts not amps, sounds to me like the motor is toasted too, (hum/heat) but i'd tear into it to check for sure if it were me, those suckers can be expensive. and ccw=counter clock wise. =o)

DM


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## 1001miles

soooo never guess what I found when I took out my draft inducer? 

2 dead birds were stuck in it & the pvc tube!!!

Everything now works like a charm -


Thanks for helping guys!!

duh --- ccw lol


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## dac122

Glad you found it. 

Seems like kids, animals and pests are sworn enemies of thos PVC pipes.


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## malim

Hey All. Just wanted to say thanks for the info.

I had the same problem and learned a little bit about furnances through my adventure :thumbup:

My motor was humming but did not seem to turn. So me and my dad suspected the motor and took it apart. It was definitly stuck. What happened was 5 of the plastic blades broke inside the motor for a reason that is unknown to us. We cleaned them out and put the motor back in and started the furnance. The motor was rattling like crazy. What happened was the blade assembly was now out of balance and was knocking on the walls of the motor assembly causing this crazy rattling. However the furnance still did not work.

We thought maybe we had two problems here and it being the pressure switch. We blew in it and it seemed fine (pop open and close). I even used a multimeter to test it and if it making a contact and it did.

So the pressure switch was not the problem.:whistling2:
We decided to bypass it and stuck a wire between the two wires going into the switch. What this does is basically makes the furnance think that the pressure switch is working, but now we had another error "pressure switch stuck closed". What i figured was that the furnance when turned on checkes the pressure switch and if it is closed (default is open) right away gives you the error code, so it doesn't get to the blower motor stage. 

What we did then was turn on the furnance and then a 1 sec later connect the two wires. TADAA!! It worked. We heat up our home because we didn't want to freeze, but then the motor just gave up and was stuck. 

I went out today and bought a new motor.:whistling2: WOW they are over priced here in Toronto. Ridicoulous prices... some people want $475 plus tax for it.
I searched around and i was given a company that sells motor by a nice guy i called while looking for the motor.
The company is called Canada Motors. Great guys.

Canada Motor & Supply Co Ltd- more info »
6 Bramsteele Road, Brampton, ON L6W 1B3, Canada‎- 
(905) 451-4474‎

Popped it in and YAY. We are warm.

Thanks everybody. Great experience. Hope i did not bore anyone here, but i just felt like giving back to the community and share my experience. If you fixed something, post it here )

:thumbup:


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## dac122

Glad we could help to get you on the right path. It sounds like with the missing/broken blades weren't pulling enough draft to close the pressure switch. If you had a vacuum pump you could have pull the hose from draft inducer, put it on the pump and pulled vacuum at the right time to fake-out the controller. 

Just curious did you have to spend the $475, or did you get a better deal at Canada Motor?


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## malim

Yeah, i had the same theory about fan not having enough power but forgot to write that.

I did get a better deal. It was $275 with tax. Not bad comparing to $475 before tax.
Make sure you ask about warranty. It seems to me these fans are very unreliable. The one that i took out was FASCO (my old one) so i figured it was replaced once already or do YORK install FASCO from the factory ?


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## beenthere

Yep, York uses Fasco's.

Many are made by fasco.


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## grimace15

*I fixed my 3 bleep light this way...*

I tried cleaning off the thermal sensor to no avail. The system would still come on, the pressure fan would blow, the igniter would glow, then the gas would start and light, then it would go out after 5 to 10 seconds, then the blower would turn.

Then I see that the 3 flashes indicates that the pressure switch is open. Ok...let me remove the tubing and see what I see. The side that conects to the fan part (not the switch) was a little clogged with rust like deposits. I thought it was supposed to look like that so I place the other end of the tube on the switch and inhaled and heard the switch...well...switch. hehe.

Let me look for dead birds first in the vent, becuase I was hesitant to remove the "rust" deposits from the other end. After removing two sheet metal screws, there were no blockages (no birds). Ok...since I have it off, I verifed the rat cage inside the exahust was turning both without the power and with and it did.

Now let me see if I can suck on the end of the tube from the switch long enough for it to fire up and have the blower start and keep it running. I was able to accomplish this by placing a straw in the end of the tube and sucking on it to close the switch and it FRIGGIN WORKED!

Now for that rust thing I wanted to remove. I got a small screwdirver and stuck it in the hole and all it was, was a little corrosion build up. IT WAS BLOCKING THE AIR FLOW! Now I took the other end of the tube connected to the switch and connected it to the fan and VIOLA! IT WORKS NOW.

Mind you, this is AFTER having a professional come out and tell me I needed a new control board. I had it fixed in less than two hours after he left the door. I am not paying for the visit as he could have done the same thing. Hell, I am just a pharmacist and thinking of opening up an HVAC training school!

I am seething...trying to cool off (no pun intended as we now have heat). Good thing the place is closed. They will get an earfull tomorrow...

grimace
aka Joe


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## kenmac

those small ports will clog with rust caused by condensation sometimes


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## beenthere

There are some techs that have no idea how a furnace really works. Guess you got one of them.


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## AlphaM1

*thakks for saving me $?00.00*



kenmac said:


> those small ports will clog with rust caused by condensation sometimes


cant believe this was so easy. it took me longer to find this forum, than to fix my furnace. 

just wanted to say thank you. and keep on posting, you dont always just help one person with knowledge, i can tell you, this site and the members are great. THANK YOU ALL!!!!!
:thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup:


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## DangerMouse

AlphaM1 said:


> cant believe this was so easy. it took me longer to find this forum, than to fix my furnace.
> 
> just wanted to say thank you. and keep on posting, you dont always just help one person with knowledge, i can tell you, this site and the members are great. THANK YOU ALL!!!!!
> :thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup:


SWEET! We can only assume you had the same problem! 
Glad you found the answer here.

DM


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## dmdonnay

*unbelievable*

I was experiencing the same problems. :furious: The furnance would run for about 90 seconds and then would shut down and give a "pressure switch stuck open or closed" error message. I tried everything you did from dis-engaging the hose and manually testing the switch to cleaning out the end by the motor.  Nothing seemed to work:confused1:; until I took off the door to the air intake and held the safety button with my hand and started the furnace. Low and behold, the furnace ran for 5 minutes without shutting off. Then I remebered I changed the filter two days ago; right when the problem started. Since the temperature is 59 degrees in the house and my wife is even colder to me since the house is so cold :laughing:and it is 2 a.m., I am running the furnace without the filter and will be getting a new filter in the morning. The house is already starting to get warmer and I will not have to have a service call on Sunday. Thank you :thumbup:


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## beenthere

Air filter has nothing to do with the pressure switch. The pressure switch is for the pressure in the inducer and heat exchanger. not for the pressure external to the heat exchanger caused by the blower or air filter.

My guess would be that you either read the code wrong. or that you disturbed the right thing when you opened the panel..


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## likediy

*Where to buy these pressure switches with fair cost?*

Anybody know where to buy these switches with fair cost? Thanks.

My switch is definitely malfunctioning. I blew and sucked the port of the switch and used my multimeter to check the connectivity of the 2 pins. I could hear the click but the meter showed numbers between 150 Ohms to 400 Ohms, which was rediculous.


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## DangerMouse

I don't think anyone sells ANYthing at a 'fair cost' any more.... sorry... just ranting....
Google the model #s and switch type and you may find them online.

DM


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## likediy

Found this one on the web:

http://www.mobilehomerepair.com/media/img/coleman/024-35286-000.jpg

Mine is -1 PF. This one is -0.9 PF. It should be working, right?

Thanks.


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## rstevens

You might hate me for mentioning this, BUT, I went the cheap way and *just replace the actual Fan Blade* for $32.00 US. The only trick is you MUST know if the fan turns CW or CCW. and the measurements. I put it an aluminum fan blade and works great!

I am the biggest cheapskate ever, so DIY is my middle name! =)


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## likediy

rstevens said:


> You might hate me for mentioning this, BUT, I went the cheap way and *just replace the actual Fan Blade* for $32.00 US. The only trick is you MUST know if the fan turns CW or CCW. and the measurements. I put it an aluminum fan blade and works great!
> 
> I am the biggest cheapskate ever, so DIY is my middle name! =)


It could be a good idea, but we have to find out how stronger suction the new blade would generate comparing to the original one... It might be hard for some DIYers...

BTW, I ordered the pressure switch shown in the link and replaced the old one. The furnace works perfectly.


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## william K

what motor or location of the motor


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## william K

*pressure switch stuck open*

The motor would humm where would that motor be located AT


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## Traida

grimace15 said:


> Now for that rust thing I wanted to remove. I got a small screwdirver and stuck it in the hole and all it was, was a little corrosion build up. IT WAS BLOCKING THE AIR FLOW! Now I took the other end of the tube connected to the switch and connected it to the fan and VIOLA! IT WORKS NOW.
> 
> Mind you, this is AFTER having a professional come out and tell me I needed a new control board. I had it fixed in less than two hours after he left the door. I am not paying for the visit as he could have done the same thing. Hell, I am just a pharmacist and thinking of opening up an HVAC training school!


***Same problem solved, different root cause to try***

I was experiencing the exact same problem but did not find any corrosive build up on the blower-side tube connection. I DID, however, hear some odd noise when testing the pressure switch by sucking/blowing on the tube to hear the "click" (it did click by the way indicating the possibility of working properly). 

The noise resembled water being sucked. I removed the pressure switch and headed to the sink. Shook the thing and wouldn't you know it? Rust-colored water started coming out. There must have been several table-spoons of water in the switch. 

I have no clue how it got in there (must have been some condensation along the life of the furnace) but after shaking it out, re-installing the pressure switch, confirming proper "switch" operation by sucking on the tube, and starting the furnace once again things seem to be working.

The water in the switch must have been causing a constant "switch open" indication.

Thank you very much for all who contribute to this forum. I hope that my issue/resolution helps at least one of you out there looking for answers!


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## biggles

the motor should never be hot to the touch even when running in the winter..but warm.so after the summer is over and the heating gets used more often,keep in mind that touch test.voltage applied to a jammed motor isn't the best thing for those windings and your continuity test was right on...white/black dead short,each to motor body infinity,each to the green ground infinity.chicken wire cap on the end of that PVC is a suggestion.removing the motor off the mounting plate and checking those squirrel rounds once a year is a good maint.:wink:


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## how

Hey Traida
This problem will probably happen again. Do you have a drain tube attached to the bottom of your ID assy that might be obstructed?

If not, having the tube from the ID assy constantly rise up to the PS, allows the forming water droplets to flow back down to the ID assy when the heating cycle ends.


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## laneuiowa77

*debris in induced blower fan outlet*

I turned the furnace on for the first time this season and nothing. I had the 3 red flashes and the manual said the pressure switch is stuck open (as noted here too). As discussed in this forum, I removed the hose and you could see debris in the outlet nipple. Removing the debris, which appeared to be rust/corrision, fixed the problem! 

Thanks a ton for the helpful info on this site. :thumbup:


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## Cheloco51

*Same problem new fix*

So, thanks to all of you I was able to test/clean/check things out. My error code said that the switch was stuck open and when I sucked on the tube(or let the vacuum take over) everything fired up and worked fine. But after doing everything suggested it still wouldn't run on its own. 
So bad pressure switch. When I took it off I noticed a screw in the middle of it. So I popped it off to find that it was holding a spring against the switch diaphragm. So I loosened it and put it back on and got the error code that the switch was stuck closed..hmm. I then tightened/loosened it until I got no error code and everything fired up/shut off properly.

So I guess that means that my pressure switch is pretty close to kicking the bucket. Just wanted to share my experience/fix since you have saved me a service call and taught me a ton.

Mahalo!


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## biggles

might of been stuck OPEN...remove the 2 wires to the PS and set your ohm meter up to read open/closed start the IDM go CCW on that adjuster screw on the diaphram so the meter reads open with the IDM running go CW slowly till the meter closes(switch is closed)slight tweek to CW and it is set.that pressure switch has to be open before a call for heat and close when the IDM starts to prove there is air intro'd into the burner section so the rest of the show can go....any break in that closed contact during a heating cycle will shut the burner off(even if the IDM is running)and restart 3X then... latch out the furnace requiring a repower on the service toggle on the furnace....


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## beenthere

Cheloco51 said:


> So, thanks to all of you I was able to test/clean/check things out. My error code said that the switch was stuck open and when I sucked on the tube(or let the vacuum take over) everything fired up and worked fine. But after doing everything suggested it still wouldn't run on its own.
> So bad pressure switch. When I took it off I noticed a screw in the middle of it. So I popped it off to find that it was holding a spring against the switch diaphragm. So I loosened it and put it back on and got the error code that the switch was stuck closed..hmm. I then tightened/loosened it until I got no error code and everything fired up/shut off properly.
> 
> So I guess that means that my pressure switch is pretty close to kicking the bucket. Just wanted to share my experience/fix since you have saved me a service call and taught me a ton.
> 
> Mahalo!


It has already kicked the bucket. Get a new one now. Cause you don't have a switch that will open when its suppose to, to protect teh furnace and you from harm.


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## Cheloco51

beenthere said:


> It has already kicked the bucket. Get a new one now. Cause you don't have a switch that will open when its suppose to, to protect teh furnace and you from harm.


Yeah, I was planning on it since I didn't know how long this would last and it is a low cost fix. So what creates the pressure that opens/closes the switch? And could that be causing the issue?


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## beenthere

The inducer creates the pressure. It can be running slow. A 50 to 100 RPM drop is hard to see by eye or even hear.


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## Cheloco51

From what I've read the chances of it actually being the pressure switch are slim. Is that correct?

Also, would I be able to tell if the inducer wasn't creating enough pressure to trigger the switch properly without any equipment?


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## cpierce811

*Pressure switch keeps getting stuck open*

I have a york diamon 90 and the pressure switch keeps getting stuck open. By blowing in the tube, it will reset the switch. Took combustion blower off of furnace, and ALOT of water came out, which fixed the problem for about two days. Did this again, and again it lasted for two days. What would be the reason water keeps filling up in there. I am completely stuck at the moment, and any advice would be appreciated. Thank you!


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## beenthere

Could be a problem with the gas valve. Need to check the manifold pressure.


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## cpierce811

How would I do that?


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## beenthere

Need a manometer.


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## cpierce811

Is there anything else that could be causing this to happen?


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## beenthere

Obstruction in the flue/vent pipe, obstruction/dirty secondary heat exchanger, slow running inducer.


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## cpierce811

The inducer motor seems to be running fine, no different than it ever has, how could I tell if the secondary heat exchanger was dirty or obstructed, and how would it be fixed?


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## beenthere

Remove inducer and inspect it. Often it has to be replaced. Sometimes they can be cleaned.


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