# Nordyne furnace, error code: Pressure switch stuck closed.



## beenthere

More like just a defective/worn out switch.


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## javagrendel

Thanks for your answer, beenthere. I had figured that because it was working intermittently, that the pressure switch was fine. I'll look into replacing it.


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## how

A pressure switch measures the vaccum created by a running inducer motor assy. When there is a call for heat, before the inducer motor turns on, the board verifies that the electrical circuit through the pressure switch is open. After the board verifies this, the inducer assy is powered and the pressure switch is pulled closed completing an electrical circuit that allows the furnace to continue onto the ignition cycle.
It sounds like you have a faulty electrical switch within the pressure switch. This whole PS will need to be changed.


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## javagrendel

I just tried by-passing the pressure switch by shorting the two wires connecting it to the main control board. The gas did ignite, but only for a couple of seconds. I tried it again, this time the gas did not ignite at all. Is it still worth trying to replace the pressure switch?


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## how

You've been describing an erratic electrical switch response in the pressure switch. 
A code that says the PS is closed when it should be open will either be a faulty PS, a short across the wires that attach to it or a faulty board.

You can use an electrical meter to verify that electrical switch in the PS is stuck closed when it should be open.


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## javagrendel

A faulty board makes sense, I think. 

I just unhooked one section of the duct so that it vents directly inside the basement. When the inducer motor starts up, I can feel air being forced out through the duct, but the gas still won't ignite. I took that to mean that it's not a problem of the exhaust vent being blocked. I also took the opportunity to inspect the duct itself, and it's not blocked with anything.

When I disconnect the two wires from the PS, the ignition sequence doesn't even start up. The MB led flashes twice, which, according to the legend on the inside of the cover panel, means "Pressure switch stuck open". Then I short the two leads using a small piece of wiring. The main board LED switches to ON (meaning it stops flashing), and the ignition sequence starts up again. (Note: if I disconnect the two leads while the ignition coil is heating up, the sequence aborts.) From this point on, the furnace behaves exactly the same as if the PS was still connected; the main board responds to the call for heat from the thermostat by starting the inducer motor. After a few seconds, I hear a click, and the ignition coil starts to heat up. When the coil is glowing a bright orange, it should ignite the gas, and then turn off. But it doesn't do that. Instead there's a loud click, and the sequence aborts. The inducer fan keeps running for a while longer, and the main board LED starts its error code flash (three flashes). After flashing the error code for a few seconds longer, the inducer motor turns off. The entire sequence begins again immediately, with the inducer motor quickly turning on again.


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## javagrendel

Ok I don't know what to make of this. I unplugged a couple of wires, blew some dust off the mainboard and connected everything back up and then restarted the furnace. It started up and now it appears to be working fine. In the picture you can see the vent flue switch that I disconnected and reconnected.


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## javagrendel

This actually happened when the gas utility tech was here. It worked for most of the day and then stopped working again. It has heated up the house to the point that the thermostat turned the furnace off again. I'll have to see how it does for the rest of the night.

The fact that it's so flaky tells me something is up with it. :-(


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## eboat

Unless you have two flu pipes going out the furnace your fresh air intake is coming from the room the furnace is in. Which means you have an 80% furnace. After the hot surface ignitor heats up you should hear the click of the gas valve opening and then it lighting the burners. I assume you have gas and your tanks not empty so your two choices would most likely be the gas valve or control board not functioning correctly both could work intermittently but sense you were getting a fault code adding pressure switch it almost sounds more like a board. You need a meter and a magnahelic to really determine the exact problem but with what we know I would replace board and pressure switch. The switch is very cheap and fail all the time so it'll be good to have that regardless. 
Good luck lol


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## eboat

Also it's hard to see to much in that picture but what you unplugged was a roll out limit. Which doesn't have anything to do with your problem your having now. It's only there to keep your furnace from being damaged or your house from burning down if the flame starts rolling back out of the heat exchanger


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## eboat

On further looking that actually might be a vent switch in the picture. But if it was tripping you'd have to Manuel reset it with that middle button right on it. So either that's Ok


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## javagrendel

According to the spec that is a vent switch. I may have tried pushing the reset button before, but I don't remember for sure. The furnace has been functioning normally since I did that. We shall have to wait and see if it lasts through the night.


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## eboat

Ok lemme know if you have any new developments its a fairly simple furnace so im sure u wont have to much trouble getting to the bottom of this. 
Gofd bless


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## javagrendel

So my furnace continues to act up, coming on sometimes and not at other times. I want to replace the pressure switch, but I'm having a little difficulty tracking down the part number. Does anyone have any suggestions as to where I might find out this information? In my original post, I linked the pdf documentation that I was able to track down, but it does not list a part number. I've tried searching in Google for key words "parts list FG6RA series furnace pressure switch" but so far I'm not having any luck. 

Any help would be greatly appreciated!


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## javagrendel

I called my local parts supplier. They wouldn't give me a price ("because we don't sell to homeowners") but they did give me a part number: 626350. Nothing else, just that number. I'm trying to track that to an actual part that maybe I can order online.


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## yuri

try americanhvacparts.com they seem to have a good site.


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## JScotty

javagrendel said:


> I called my local parts supplier. They wouldn't give me a price ("because we don't sell to homeowners") but they did give me a part number: 626350. Nothing else, just that number. I'm trying to track that to an actual part that maybe I can order online.


The number they gave you looks to me like it's the limit switch in your picture not the pressure switch.


http://www.ebay.com/itm/Nordyne-626350-Limit-Thermostat-Manual-Rollout-/130827954839


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## javagrendel

I know, JScotty, I'm confused by that part number too... The lady on the phone seemed quite impatient with me, so I didn't press the issue - I figured I was lucky to be getting any info at all, as I am not a licensed HVAC tech.


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## javagrendel

I'm not at home at the moment, but when I am, I'll look up the part number on the one that's in there now and see if I can look up a replacement. I had that info written down on a piece of paper for reference, but that was last week.


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## javagrendel

Thanks for the suggesting americanhvacparts.com, Yuri. I couldn't find an exact match, but I've sent them a parts request via their website.


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## yuri

Yur Welcome.


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## EPKA

I seem to be having a similar pressure switch problem. Did you get this part for your furnace? My book lists the pressure switch part number for G6RA096C-16 Nordyne Intertherm furnace as 632252.


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## bkoverhere

Hey,
I am having the same furnace issue that you described in 2013. I have replaced the switch only to have the same fault occur intermittently. Can you tell me how you fixed your furnace? Did you replace the circuit board or have to replace the hole furnace?
Any help would be appreciated. 
Thanks


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## bkoverhere

Hey,
I am having the same furnace issue that you described in 2013. I have replaced the switch only to have the same fault occur intermittently. Can you tell me how you fixed your furnace? Did you replace the circuit board or have to replace the hole furnace?
Any help would be appreciated. 
Thanks


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## supers05

bkoverhere said:


> Hey,
> I am having the same furnace issue that you described in 2013. I have replaced the switch only to have the same fault occur intermittently. Can you tell me how you fixed your furnace? Did you replace the circuit board or have to replace the hole furnace?
> Any help would be appreciated.
> Thanks


Use a manometer to check the vacuum at the switch. They are cheap enough for the DIYr. Chances are that you have plugged venting or heat exchanger or a dying venter motor. 

https://www.amazon.com/dp/B00N3PPZZY/ref=cm_sw_r_cp_awdb_p7XIzbME8F36X

Cheers!


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## bkoverhere

Pressure is good and steady and I replaced the switch as well to rule out it being the intermittent failure.


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## roughneck

bkoverhere said:


> Pressure is good and steady and I replaced the switch as well to rule out it being the intermittent failure.


What was the exact pressure you measured on the exhaust, and what is the switch rated for?


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## bkoverhere

I believe the switch operates at .65-.7"wc and I was measuring 1.25"wc.


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## supers05

bkoverhere said:


> I believe the switch operates at .65-.7"wc and I was measuring 1.25"wc.


With or without the furnace firing? It changes on firing and then as condensate starts to form. (if any at all.) 

Cheers!


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## bkoverhere

I will have to reconnect to see. If there is condensate then what would that imply? Cracked heat exchanger or blocked vent?


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## supers05

bkoverhere said:


> I will have to reconnect to see. If there is condensate then what would that imply? Cracked heat exchanger or blocked vent?


You should see condensate. Those units are designed to avoid it, however when setup wrong can condensate a bit. It'll rust out the heat exchanger and venting. 

You should see a higher pressure (less negative pressure) after it lights off. Let it run for 10 min (or as long as it will run) Keep watching the manometer.

Cheers!


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## bkoverhere

Thanks for responding Super05.
The unit is about 20 yrs old. I replaced the the chimney brick (flue runs thru it) not the flue piping to the chimney about 5 years ago. I replaced a faulty T-stat about 10 years ago. This issue started this spring. So, from your previous comment I gather that the exhaust vent could be compromised (perhaps due to age). I have not altered the exhaust vent system other than chimney brick replacement. I'm assuming the system was set up fine (its worked for 18+ years) . Any more info would be gretat


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## bkoverhere

Thanks for responding Supers05.
The unit is about 20 yrs old. I replaced the the chimney brick (flue runs thru it) not the flue piping to the chimney about 5 years ago. I replaced a faulty T-stat about 10 years ago. This issue started this spring. So, from your previous comment I gather that the exhaust vent could be compromised (perhaps due to age). I have not altered the exhaust vent system other than chimney brick replacement. I'm assuming the system was set up fine (its worked for 18+ years) . Any more info would be great!

I fired up the unit this past week and there was no evidence of condensate in the vent or tube. The unit actually cycled about 3 times before the failure occurred. The idiot light still indicates the "switch is stuck closed". Since the switch has been replaced and I physically measure it open then it seems that at this point the board has a intermittent failure. Anymore advice would be great.


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## supers05

bkoverhere said:


> ... Since the switch has been replaced and I physically measure it open then it seems that at this point the board has a intermittent failure. Anymore advice would be great.


I somehow missed the message before. Anyways, if it's measured open, there's a problem. (it needs to be closed while the venter motor is running) 

Have you physically checked to make sure that there are no nests or other debris in the chimney? 

Cheers!


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## bkoverhere

Thanks for the response. Sorry I was not clear. The switch makes when the exhaust fan is on and breaks when the fan is de-energized as intended. I did not see any obstructions when I examined the flue. If there were obstructions further up the chimney wouldn't it affect the pressure reading? Thanks for your help.


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## supers05

bkoverhere said:


> Thanks for the response. Sorry I was not clear. The switch makes when the exhaust fan is on and breaks when the fan is de-energized as intended. I did not see any obstructions when I examined the flue. If there were obstructions further up the chimney wouldn't it affect the pressure reading? Thanks for your help.


Then yes, the circuit board is the next logical step. 

Cheers!


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## user_12345a

You should identify the pressure switch circuit at the circuit board connection, disconnect the cable and ohm out the right pins on the molex connector for that circuit.

There could be a short in this circuit or another pressure switch you're missing.


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## supers05

user_12345a said:


> You should identify the pressure switch circuit at the circuit board connection, disconnect the cable and ohm out the right pins on the molex connector for that circuit.
> 
> There could be a short in this circuit or another pressure switch you're missing.


It's wired direct. Nothing but some wire and the connector to the switch. It's possible, but somewhat unlikely. 

I've only seen that once (in resi applications), where a safety wire rubbed through and shorted to ground. To have 2 spots rub though, be touching each other, but not grounded is fairly unlikely. (if they conduct to ground, you'll blow the fuse.)

Cheers!


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## bkoverhere

I replaced the circuit board and the problem is fixed!
Thanks for your support Supers05!


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