# Carrier 59SC2A Error 31



## ahrens (Apr 11, 2011)

The airease furnaces that my company installs are having pressure switch problems with furnaces in that date range. I would replace the pressure switch and give the flame sensor a good cleaning with some grit cloth.


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## old_squid (Oct 31, 2012)

Since it's install, has it been serviced by the installer or another company?

With the main door off that is for the burner compartment will the furnace run uninterrupted until the thermostat is satisfied? And if it doesn't.....
does it sound like there is water inside of the fan housing or that it's sloshing a lot of water with the fan just before it quits and gives the 31 code?

Did you clean out the drain lines to make sure the furnace can get rid of the water it produces?


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## one.relic (Feb 25, 2015)

old_squid said:


> Since it's install, has it been serviced by the installer or another company?
> 
> With the main door off that is for the burner compartment will the furnace run uninterrupted until the thermostat is satisfied? And if it doesn't.....
> does it sound like there is water inside of the fan housing or that it's sloshing a lot of water with the fan just before it quits and gives the 31 code?
> ...


I have not had it serviced by anyone since moving into the house in September 2012. The only service that has been done in that time frame, is the regular filter changes, and the work that I have done trying to resolve the issue in question.

When the door to the burner compartment is off, the unit does seem to run longer than when it is on, but saying that, it also seems random. When working on it yesterday it would average 4-6 minutes with the door on, and about 16 minutes with the door off. Working on it today, it seemed to be only about 12 minutes (give or take) with the door off, but I was able to get it to peak around 30 minutes with the door on. Other than the overall symptoms, I have yet to find a specific pattern to the time(s).

There is a point where it will eventually run until the thermostat is satisfied, but it takes a lot of coaxing, and power cycles, to get there. There hasn't really been a point (either yesterday or today) that it ran completely uninterrupted until it hit the preset temp from the thermostat.

When the inducer motor kicks in, it does sound like there's a little bit of water in that area, but within a few seconds of it running, I can hear water being expelled by the drain pipe, and I can see it coming out. As far as hearing it before it quits, I have not heard anything that sounds like a lot of sloshing water. It will simply kill the burners mid-fire, start flashing the 31 code, spin the inducer down, and then spin the blower down. Once the system has wound down and been still for a few seconds is when the combustion process will start again.


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## yuri (Nov 29, 2008)

I would replace the pressure switch. The ONLY way to know if it really is the switch is to put a manometer and tee in the hose that goes to it and see what the vacuum is and compare it to the switch rating. The switch is not expensive and a good manometer starts at around $150.


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## one.relic (Feb 25, 2015)

Thanks for all the help with this so far everyone, I truly appreciate it.

Of course the furnace made me a liar shortly after posting this, as it worked all night last night without any issues... :furious: It didn't have to put much time in though, since the house started out at 64, and stayed a pretty even 65 all night with short kick ons to bring it up to temp.

That being said, I'm going to start looking for parts for the pressure switch. I found one place that I may be able to buy one locally, but there's not a whole lot of parts sellers near me. Does anyone have a recommended place to purchase one (possibly a big box store, or more localized place), or a good source online to get one?


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## yuri (Nov 29, 2008)

americanhvacparts.com or supplyhouse.com

with Carrier you need the COMPLETE model and serial and series # for them.


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## one.relic (Feb 25, 2015)

I actually found a local place that may have pressure switches available, but I don't have all of the info needed to get me an accurate lookup (since I'm at work). The guy had a recommendation of looking further at the draft inducer. Since I've gotten quite a bit of amazing advice from everyone on here so far, what would general thoughts be in relation to that being the possible cause of the issue?


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## yuri (Nov 29, 2008)

very likely. they are cheap plastic and built in the cheapest off shore plant they can find. costa rica one day china the next. years ago they lasted for 20 yrs or more along with capacitors, nowadays it is a guessing game as to how long they work.


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## brevor (Jan 17, 2015)

I have almost the same model furnace this problem has happened to me a few times. I took off the rubber coupling from the inducer fan to the exhaust pipe. I then turned off the switch on the gas valve and turned on the power to the furnace. When the inducer fan starts it may blow some water out the open vent, i had a rag ready to catch it. After i put the rubber coupling back on i took the hose off the pressure switch and blew back through the hose into the inducer fan housing. Doing this seems to have "fixed" it 2 times. It's been a few weeks and it has not reoccured. There is a service bullitin on this furnace for this problem that involves removing the inducer assembly and drilling out the port where the hose from the pressure switch connects. You should be able to find the procedure online. I havn't done this on my furnace yet. I also plan to clean the condensate trap but i need to find a source for a new gasket first.


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## HVACTECH96 (Oct 16, 2012)

You are probably going to need a new inducer assy.We have had quite a few issues with the bryant version.Found problem seems to be starting around 2 year mark.Not pulling enough vac to keep pressure switch closed.The motor should pull around .8" or more with door on.Finding a lot only pulling .45" and less.Pressure switch opens at .45"Also has been changes in hardware for circuit board that changed the lockout from pressure switch trips.Old ones can lockout from three trips even if they were during different cycles.Now there has to be three trips in one cycle to cause a lockout.


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## HVACTECH96 (Oct 16, 2012)

Also the drilling thing seemed to work for awhile but i've replaced a few that have been drilled already.


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## yuri (Nov 29, 2008)

Getting to be a LONG kinda boring Winter. Hard to diagnose pressure switch issues w/o a manometer and few DIYers have one.


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## brevor (Jan 17, 2015)

OK I had the Carrier guy out today, turns out there are 3 different service bullitins for code 31 faults with this series furnace. One is a new pressure switch that has a lower trip threshold. 2nd is a new draft inducer assy. that has a different casting that doesn't hold water. 3rd is a new control board with different software.


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## yuri (Nov 29, 2008)

what do they plan to do?

Carrier should pickup the tab if it is a design issue.


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## brevor (Jan 17, 2015)

Carrier took care of it.


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