Hi,
My 9-year-old Bryant 355MAV shut off after heating for about 15 minutes, even though the house is only about 60 degrees. I've been trying to figure it out all day.
If I turn the furnace off, then back on, it will start up OK, the inducer motor starts running, the burners light up and the blower runs for a good 15 minutes or so.

Then I start seeing an error code in the little LED lights. Most of the time it is 31, but one time it was 32. The whole thing shuts down. It will try to start up again a couple of times, but the ignition won't light the burners. After a couple of tries it quits all together until I turn the furnace power off and start from scratch.

My owner's manual says the 31 means a high pressure switch fault that indicates high pressure switch is closed at call, or in low heat, or fails to close after call, or opens in high heat. And it says to check for plugged condensate drain, water in vent piping, improper pressure switch wiring or pressure switch tubing connections or failed or out of calibration pressure switches.

Water in the vent piping sounded like the most likely candidate, as we just had a big sleet/snow storm yesterday. I went outside and there is definitely moisture around the opening of the vent (exhaust )tube, but the tube is curved, and I can only see in a couple of inches, not sure how to check the elbow.

As far as the condensate drain, I have no idea what this is.

I am not a mechanic, but can do simple fixes. I'm sure I can check the vent pipe if someone has any idea how I can do it, and also check this drain. Beyond that, I'm not sure.

Thanks so much for any help at all. I hate to spend my kids' Christmas money on a repair call unless I really need to.

Could be a few different things really. Inducer could be failing, pressure switch can have moisture inside etc etc.

I assume you have a high efficiency furnace?

Hi,
Thanks for the response. Yes, it is a high efficiency.
I turned off the circuit breaker and restarted the whole thing. It ran for about an hour, though the air coming out of the register didn't seem to be as warm as usual. Then it stopped even though the house was not at temperature yet. It has since cycled on and off a couple of times for 10 minutes or so at a time.
So odd.
Something could be failing. The inducer motor seems to be taking several seconds to get up to speed, don't know if that is usual.
I was just outside looking at the exhaust vent and air was blowing out pretty strongly at me. Smelled a little like exhaust air, I guess that is normal.

Is there Two pipes outside?

Hi Hvac

How's it going?

Oops, Hi HVAC
Yes, 2 pipes
The intake vent also looks clear. That one points down towards the ground (both come out the side of the house around waist high) Hard to see how it could be plugged, but I did look inside it.

I was sitting watching my furnace run. I noticed it ran for a long time, 30 minutes or so, in the green LED mode. Then it speeded up the blower fan and went into the yellow LED mode, which I think is high heat? That seems to be what triggered it to shut down.

I got the 31 or 32 code, sorry forget which, the burners went off, everything turned off, then about 3 minutes later it started up. Still running I think, about 10 minutes later.

House is up to 62 degrees, which is the warmest it has been all day. But the heat coming out of the registers seems to not be as warm as usual.

Have you looked at the chart to see what the codes mean?

I'm guessing that you're furnace is 2 stage variable speed blower.

Hi,
Yes, the codes 31 and 32 are similar.
My owner's manual says the 31 means a high pressure switch fault that indicates high pressure switch is closed at call, or in low heat, or fails to close after call, or opens in high heat. And it says to check for plugged condensate drain, water in vent piping, improper pressure switch wiring or pressure switch tubing connections or failed or out of calibration pressure switches. 32 is high pressure switch fail.

I'm sorry. I'm getting sleep deprived. 32 is low pressure switch fault. 31 is high pressure

Ok,do you see both pressure switches?

The furnace says it is a Bryant plus 90 high efficiency (natural)
Condensing gas furnace

The pressure switches are the twin round pancake like things, I see them.

Ok, do you see the rubber tubes on both of them?

Locate where the tubes plug into the furnace and remove the tube and try to clean the hole out,you will need a paper clip or something small.

I see a black rubber looking tube that goes into the side of one of them, and a u-shaped rubber tube where one end goes into the front of each of the round pancake things. They have little clamps at the point where the rubber meets the switch.

I take the tube off at just the end that goes into the furnace? I'll go look and see if I can find that. Then I just take a paper clip and clean out the end of the tube, or should I take it off both ends and blow through it?

Leave it connected at the pressure switch,remove the tube where it plugs into the header plat on the furnace.

OK, going to do that now. I'll be right back.

I'm going to take you through a few steps and see if we can figure it out.

Any luck?

Hey Hvac
I did what you suggested, took the black rubber tube off the furnace, and water poured out of it, and also came out of the furnace front. It is still coming out, so I want to go back down there, I have it going into a little water bottle.
I was surprised to see water coming out. Did I do something wrong?

At least the water is nice and warm.

OK, I think it is done draining. I think at least 3 cups of water came out of the front of the furnace.
Do I plug it back in now?

No,you unhooked the drain not the pressure switch tube,but that's OK

Try blowing through the tube you have unhooked,is it restricted?

The pressure switch tube is about a 1/4 inch rubber tube. Lets skip the pressure switch for now. Hook the drain back up.

Oh,
I tried to blow through it. I heard a tiny pop, then nothing. I can't blow through it.

What is the other end connected to?

It comes out the back of the pressure switch and goes into the front of the furnace right at the bottom of the main compartment, it goes into a flat black plastic plate that is on the front of the furnace.
I didn't see another tube that went from the pressure switches to the front of the furnace. Maybe I'm not understanding what you mean.

I'm looking at my diagram of the furnace. The tube come sout of the back of the pressure switch, goes to the side of the heat exchanger I think it is and plugs into the wall that is at the front of the furnace, right at the bottom, inside the main compartment. I wish I could upload a picture so I could show you.

Do you see the inducer fan? Located in the top compartment of the furnace.

You can upload a photo,that may help.

Is that the big round plastic cover right behind the inducer motor? I see it

OK, let me geta good photo, b right back

Do you see any small tubes going to the inducer fan?

Hi,
I have my photo, don't see how to upload it. Let me go look at the inducer fan again. I don't remember a little tube.

Hit the go advanced button at the bottom, you cadd attachments

The pressure switch is a small round part,it has two wires running to it with a small rubber tube attached

Hi,
No tubes going into the inducer fan at all, at least not from the front or sides. There is a place at the upper right corner where you could put a tube in. In the manual it says this is where you pour tap water to prime the system drain before you start the furnace, but there is no tube in there now. I see a little drop of water in the hole, which is open. No plug in it, as I think there is supposed to be.

I've attached the photo. The disconnected tube is hanging out the front of the furnace, and in the lower left hand corner of the main compartment you can see where I plugged a little wad of white paper towel into the hole in the front of the furnace. That tube comes out the back of the pressure switches.

The two silver round parts with a tube between them is the pressure switches. Reconnect the drain.

Here is a pix of the whole front of my furnace.

Sorry, a little fast on the trigger. I reattached the hose.

The small rubber tube hanging in the front,where was it connected?

You see that kind of u-shaped tube that goes into the front of the pressure switches? If you look at the back of the pressure switches, there is an identical little u-shaped hose, but there is a t-connection in the middle of it and that tube comes out the back, and the other end goes into the front of the furnace where the paper towel is.
I didn't see any other tubes from the pressure switches that went into the front face of the furnace. The one that comes out the side and goes upward is plugged into what looks like the part that brings gas into the furnace.

Ok. Put all of that stuff back together. Next, check the intake and exaust pipes from the furnace all the way to the basement wall, make sure there are no bellies in the pipe that might be holding water.

Will do. Be right back

Hmm. Both pipes seem completely straight to me. It is a pretty long expanse, about 20 feet maybe, from the furnace to the outer wall. The pipes are supported by hangers, which sounds goofy, but it all looks very solid to me.
I was outside and could see nothing in the tubes. The tubes are 3" diameter, pretty big.

Ok, should be fine then. How long has it had this problem? And does it always give you the same code?

Now that the tube is back in place, is it OK if I turn the furnace back on? It is getting kind of cold in here.

Well, let's see how it does tonight since you drained all of the water out of it,I will check back with you after work tomorrow to see how it did. It's late here and I need to get to bed.

Yep, turn it back on

No, mostly it gives me 31, sometimes 32. Once or twice it gave me 42, which means blower calibration fault, but mostly it is 31 and 32.

This problem started sometime in the middle of the night last night. When I woke up it was 59 in the house. I have the thermostat set at 65 late at night. That night we also had a snowstorm with a lot of wind.

Thank you so very much for your help. I appreciate it. Sweet dreams.

And it hasn't ran right since?

Correct. Go to sleep! I don't want you to be without sleep tonight. We are in the same time zone, it is late for you to be up if you work mornings.

Good morning,
I'm heading into work myself this morning, but thought I'd mention how the night went. It is working a little better. The furnace will cycle into the low heat mode and run for quite a while, then it steps up into the high heat mode, where the blower blows harder. It used to be that would kill the furnace, as soon as it would switch into high heat mode it would get the 31 code and shut down. Then maybe make a few more starts and quit.
Last night it ran in low mode fine, went into high mode, then got the 31 code, shut down. When it started up again, it ran in low mode then went successfully into high mode for at least 20 minutes. Stronger airflow, hotter air coming out of the registers.
But now it is back to the same problem, though it seems to run a little longer before it gets the 31 code and shuts down.
The house is staying a little warmer, 63, as opposed to 59 last night.

I have to go to work in a bit, will be home in the pm.
Thanks for giving this your thought.

Just checking in,I'll check back shortly to see if you are around.

Hi my friend,
I was wondering if all that water that drained out of the collector box last night when I took off the pressure switch drain tube indicated that maybe the drain trap or some part of the drain tubes were clogged.
Im not sure how to clear out the drain trap.
Just to test this idea, when I got home I took off the same tube again, the one from the pressure switch to the collector box. Again, water flowed out of the tube and the collector box, 2 cups at least.
Then I took the inducer housing drain tube off its drain plug. Nothing came out there.
I am thinking there should not be so much standing water in the collector box, something must be stopping it from draining. Does this sound right to you?
Do I need to go to the drain trap now?

The trap should be flushed at the beginning of each heating season as part of the required maintenance for the unit. If you experienced condensate migrating through the pressure switch tubing, the switch canister may have water inside and will eventually fail. Take the pressure switch off and give it a shake to see if water comes out. If so, I highly recommend replacing it. And, you're correct about water accumulating in the collector box-this is a sign that it is not draining properly.

Sounds like too much water your trap is the white thing at the bottom of you pic. It hangs down into the blower compartment. Take it off and clean it out with water. And the hose coming off that going to the drain clean that out (flush water or blow it out)

Hi,

I think I got it, thanks so much for the invaluable help. Until I found this site, I was really bummed. I just did not have it in my budget for a $300 service call 2 weeks before Christmas. Would have been pretty thin pickins under the tree. Your helpful advice gave me the confidence to do it myself. Now I feel pretty handy.

Couldn't figure out how to get that drain trap out, so I took off the biggest tube, the collector box drain tube I think, and blew a bunch of water through the drain trap. I got a bunch of gunk out and when it seemed clear, I put the tube back on.

Turned on the furnace and it so far seems to be working fine.
The first 10 minutes or so it ran, a gurgling sound came out of the drain tube, but it quit after a few minutes.

KC13, I don't feel confident enough to take the pressure switches off, but since the furnace seems to be running OK, do you think it is OK if I wait until spring to make a preventive service call? Christmas and all that...

Greg HVAC guy, do you work the northern suburbs, like Highland Park? That's where I am. If so, give me your co name and I'll call you then.

Than

The question you must ask yourself is, do I feel lucky? Well do you? C'mon man, you've come this far, check those switches! If you look closely at the pressure switch hoses, they should have labels to identify where they go. The switch assembly mounts to the front of the inducer with two 1/4" zinc-plated screws (yellowish color). Take 'em out, pull the labeled hose off the tee in back, and shake the switch assembly. If you hear water inside, drain out as much as possible and replace the switch assembly as soon as possible. If not, then answer yourself-yes, I do feel lucky!

Well, it is supposed to warm up this weekend, so I guess I could shut the furnace down for an hour or two.
When you take those screws off, the 2 switches and the bracket all come off in one piece? I don't have to take the wires off the front?
If I hear water, I'd drain it out the holes where the rubber tubes connect, I guess?

Yes, the switches are an assembly. If one is bad you replace both. No need to remove wires yet, just the screws and the hose on the back so you have enough movement to detect water if present. Confidence! Or draw a pic, works just as good...