ERROR CODE 33 - Troubleshooting a Bryant Gas Furnace 

Lol “for some dumb reason” is the best relatable statement in a help video

Three times in the past two years this video has helped me! The first time: The fresh air intake was clogged with debris. The second time: We had sustained high winds that affected the exhaust. The third time (last night): The air filter was due for a change. It wasn't terribly dirty, but this HE furnace requires more airflow than what the ductwork was designed for (with the original furnace), so it is more sensitive to a dirty filter. Thank you very much!!

I'll add my comments in case it helps anyone else. I had the error code 33 and issue of no heat but blower/fan was working fine. My son was an HVAC tech in the Army so I enlisted his help. I had the manual and we looked at everything that was related to error code 33. We re-set all of the re-settable switches and even ohmed them out with a multimeter to make sure they were good (looked at the schematic to determine if they were normally open or normally closed). Made no difference. Also ohmed out the ignitor; it was good too. Still the ignitor would not come on. We looked at the control board and found no voltage where the control from the thermostat was supposed to be. Well my son then had the idea to go outside and check to see if the A/C unit came on when I switched the thermostat from Heat to Cool. Well that would have been a timesaver to have checked that first! it turns out. Because the A/C unit did NOT turn on. So that indicated the problem was not in the furnace unit at all, it was with the thermostat. I found a manual online for the thermostat and it suggested for the no heat problem to clean the pins (with a pencil eraser) and contacts of my unit, which pulls off the wall for access. So I did that, then turned on the furnace again, and voila! ignitor glowed orange, then the gas came in, and had flames and heat once again! So the poor connectivity of the pins/contacts in the thermostat unit were the culprit. Hope that helps someone!

My issue with error code 33 was the gas pressure to the furnace was too high. We had some gas lines and gas meter replaced as part of a house renovation. My HVAC guy noticed the flames in the furnace were irregular and not blue enough. The plumber came back with a manometer, made the necessary adjustments, and the problem was solved. The flames are blue and uniform.

I am having this problem and my technician came 4 times yet could not resolve it. Finally trying myself to resolve it by doing some research. Your video was very very helpful. Cheers!!!!!!!!

I finally got the 3-3 error fixed after watching this video and reading the comments. I had two issues 1) a part failed 2) improper furnace sizing. I replaced all the parts except for the gas valve for $900, since it was 15 years old, now it's basically a new furnace. I thought this was better than spending $7,000 - $9,000 on a new furnace, which is what the HVAC companies suggested. Unfortunately I still had the 3-3 error. After reading about the proper furnace sizing comments here, I realized the furnace produced twice the amount of BTU for the sq footage. I remembered when I first started to troubleshoot this issue I turned off the gas ball valve, then later turned it back on realizing it wasn't necessary. I believe the gas valve was originally partially closed to restrict the amount of gas, so I slowly closed it watching the flames decrease in size. This solved the second cause of the 3-3, by limiting the amount of gas of an improperly sized furnace, it no longer produced too much heat to trip the sensor. The HVAC company would have replaced the furnace with a properly sized unit and it would have worked, I don't think they would have partially closed the gas valve to compensate for the oversizing and lost a $7000 new furnace sale. Hope this helps someone else in this situation. Now i'm going to replace all the furnace parts in the 15 year old furnace on my second level.

Impressively thorough. I've been going round and round with the tech who just wants to swap a control board, which was swapped once already and highly doubtfull to be the issue for this code. I question the thermostat because it comes and goes, just seems to stop early, but it does trip 33. Another thing I was wondering about was about that limit switch you show, one other guy said that can fail, and even test okay, but due to age will trip prematurely. First, I'm going to take your advice and make sure all registers aren't blocked.

Thanks for the video; mine was simply a loose connection on the heat sensor/limit switch. All I had to do was plug it back in. You know, now that I think about it the heat had been short-cycling for some time and it was probably losing contact with the switch! No emergency heat repair for us!

Thank you. Took me a while to find your vid. After I saw it. I went down to the furnace removed the other side panel and the limit switch never tripped. So I built a similar filter system as you did and the furnace has been working fine for the last 2 months. I did all the checks the YTube, so called engineers, explained. They were a waste of time. No bird or mice anywhere found, all the vents are clean as well, nothing in the exhaust pipe, bla, bla, bla. Nothing at all found wrong. I even checked the motor capacitor and speed all within normal range. Your fix did the trick and save me from having to buy another furnace. Thanks again for sharing this great fix. It worked for me. Have a great Christmas. Mike Di Feo

The best way to see if the ductwork is supplying enough air is to measure it and in this situation I would measure the static pressure to determine if it was the return or the supply at fault. I'm almost willing to bet that original installers had panned the joist space for use of the return air and somewhere there is a restriction. Low return maybe fine for an old steel or cast iron heat exchanger furnace but will not work on any of the new style furnaces no matter the brand name or type. This is not a bad design of the furnace, i've installed many of these and as of yet i've had no call backs do to the problem your having, but I make sure that the airflow is spot on. (if you're not testing you're guessing) is a phrase that I tend to say a lot, but its the truth. If everything is right, you can pull from one side of the furnace with the exception of a 5 ton system, then you will need to pull from the bottom or both sides, you will need to check with the manufacturer to see what they recommend. Anyways i'm glad you got it running!!

If your furnace was tripping on the manual reset MAIN high limit switch and not the manual reset vent draft safeguard switch, then yes I would have to agree that your issue will be either insufficient airflow or over-firing. How you arrived at your resolution may lead others to believe they have a ducting problem which may or may not be true. You should always ensure you have a clean filter and that all the supply vents are open and unobstructed before attempting any skilled troubleshooting. Your furnace rating plate lists the temperature rise range as 50-80 degrees F. which is specific to your model furnace (310AAV048135) This range adjustment is done by adjusting the blower fan speed only after the firing rate (gas manifold pressure) is 1st adjusted with a water manometer. Once the firing rate is adjusted (based on the calorific gas value table in the installation instructions) then the temperature rise (airflow) across the furnace heat exchanger maybe adjusted. This temperature rise should be mid-range on the rating plate which for you specific model furnace would be 65 to 70 degrees F. The temperature rise is measured at the return air entering and the supply air leaving the furnace (before any cooling coil). Other issues that can give you insufficient airflow is the cooling coil insulation coming unglued and blocking the airflow across the coil. On properly designed & installed duct systems they install dampers so to properly adjust air flow to the room(s). Possible that someone has moved or closed off the damper(s). After all of this...I would have to agree with 30248abcd that your vent pipe for your flue is NOT to code and that can also cause you to nuisance trip on a code 33. That is another lesson for another day. I hope your furnace is functioning fine for those cold winter days/nights for it is a well designed product and should give you reliable service for years to come as long as it is sized, installed & service properly.

I like what you did and that did fix the problem but you i would had check something else before doing a new return. Check your gas valve, if allowing too much gas for little oxygen you have your flame will get too hot and that will trip your limit switch. Turn down the gass pressure for proper combustion. You need a manometer for this.

The immediate question that comes comes to my mind is how long has this furnace been in service with absolutely no issues whatsoever? This would indicate all the extra work installing an additional air inlet was not probably not necessary or recommended. First thing to check the temperature limit switches, second thing to check that the chimney stack is completely free and clear if all blockages such as the birds nest as mentioned in the comments below. Temperature sensors are only expected to last for a certain period of time do to the thermal expansion / contraction work that they do on a daily basis over time. Someone needs to get a meeter out and do some measurements for some restless trouble shooting.

Great video! Thanks much. I did not know these furnaces (mine is a Bryant 310JAV) have error codes until I watched your vid. I also was receiving error code 33 for a limit circuit fault. It acted exactly like yours, running the burners for about 3 to4 minutes then shutting down. Turns out I had an open (OL) capacitor. Way out of the ball park. Should have been 7.5 uf give or take 6%. Replaced the cap and works great now. Sure beats having to swap out the blower motor! Not sure why I have medium speed (BLU) and high speed (BLK) wires on this furnace. When I tested for current, only the low speed (RED) wire had current. I don't have central cooling or any control over the fan speed. I wonder if the controller adjusts the speed of the blower depending on how hot it gets. Once again, thanks for your vid, very informative. Got me on the right troubleshooting path.

Light blinks[ ooo o o o] through the round window on the furnace cover which translates to error code 33. and means there is a blockage in airflow. Start with your air filter. Take it out. When I did mine, I couldn't even see through it. Pulled it out and works like a charm. Also brush off the front of the burners and the gas outlet ports with a tooth brush while you're in there, Should end up with nice clean blue flames. Now, all I need todo is get a new air filter with less air restriction. A 3M high end air-filter did this to me. Also... To test the thermostat, pull off the thermostats cover plate. Then jump the red wire to the white wire(HEAT). If the furnace goes on and does the same thing, it is not your thermostat so you wont need to waste your money on buying to buy a new based on a hunch. Hope this will help someone. Was going crazy for three days when it was -13 degrees outside. Mmm Mmm Mmm.

just fixed mine thanks to your videos...Blessings to you

First I'm not a qualified HVAC tech. But I've read the manuals on all the furnaces I've ever owned (dozens). If indeed this furnace had inadequate return ducting it would show up in a static pressure test. Your furnace should have two tests done to assure proper installation: static pressure and temperature rise. A static pressure test can be done with a U tube manometer. You can make one with a 6 inch ruler and a length of quarter inch plastic tubing. Put the tubing into a U shape with the apex down, no kinks and staple it in place on a board. Put some water in the tube and mark where the water level is on both legs of the U. Then drill a hole in the return and supply plenum and put one end of the tube in such that no air leaks around it. Something sticky like chewing gum may help seal the tube. Measure the water deflection in the blow and suck sides. One will be above the line and the other below, i.e. positive pressure on supply negative on return. Add them together and the sum should be something like 0.5 centimeters. Modern furnaces need to "breathe" so replacement furnace may require duct rework to get the static pressure into proper range. Temperature rise can be adjusted with blower speed if static pressure is ok, but static pressure needs matched and adequate flow across the blower. Also a damaged secondary heat exchanger can cause a high limit switch to open, causing short-cycling. I would always check this first.

I’m betting it is your high limit switch that is faulty. If the furnace was running fine before you cut in the extra return air hole chances are it was getting enough return air, this usually means the high limit switch is bad and tripping to soon.

Good Video! My problem ended up being a dirty filter that actually started to warp inward from the suction of its clogged pores. Had to take off the bottom panel to reset the blinking sensor light instead of waiting the three hours the system would automatically retry...

also you need to check gas pressure there is a recall on the gas valves for letting too much gas through on those furnaces which causes them to get too hot and trip the limit

I got the code 33 today. I replaced the flame sensor. It didn't work still. I replaced the filter. It was very very dirty. After, it is working fine now. Thanks for the tips.

Had this code on my furnace too. Identical looking furnace but a Carrier 15 yrs old. Turns out it just needed a new air filter. I was using one with too high of a MPR/MERV rating and was getting clogged - after about 5 months. I changed the filter to a lower rating of ~600 MPR. Problem solved. I've learned that high rated ones are not necessary and just force the air blower to work harder/less energy efficient. The filters are primarily to protect the blower. Secondarily for better air quality.

Problem #1 - The system is oversized because no load analysis was done prior to selecting the furnace. Problem #2 - The installing company not only oversized the furnace but they can't read either. The installation manual clearly states that for all furnaces of 100,000 Btu input or greater, the unit requires dual returns consisting of one side (not the back of the furnace), two sides or one side plus a bottom return. The furnace installed has a 4.0-ton (1600 CFM) blower rating and a 135,000 Btu input gas rating. We service and install furnaces in huge homes but invariably they all need multiple, smaller units due to structural limitations on running ducts. I really doubt you home needs 108,000 Btus of output from that furnace. The end result is short cycles, short heat exchanger life and low comfort from hot/cold/hot/cold short cycling. It's not a design flaw by Bryant/Carrier, it's an installation failure of the first degree.

I was totally hoping the camera would get sucked into the blower. Great video, though. It woulda been nice if you had gone into how to check the tripped-ness of each of the sensors while the furnace is in a failure/overheat state, but... that's easy enough to google separately. Thanks for the vid.

should not cut a return inside the furnace room where the exhaust vent is. Now gas fumes can be pulled into the return and sent upstairs.

It’s more of an installation issue not sizing vents correctly The problem you made is you said the second air return is pulling air in from the basement, not a good idea because now it’s pulling the cold air from basement and any other chemical fumes or possibly exhaust from the water heater draft hood. Your other ideas and tips are good info

You are the man resolved my issue

nicely done, lot of comments are not approprite. trouble shooting intermitting problerms are tricky . accumulated comments are helpful

If you get a code 33 on one of these Carrier units (I have the exact same model in this video) its usually a filter or high limit switch issue. First take the filter out flip the power switch off on the side of the furnace for about one minute turn it back on and let the furnace cycle for about one hour without the filter and watch the code LED for steady or blinking. If you are still having an issue and you can hear a pop sound followed by the burners shutting down replace the high limit sensor its cheap and easy to replace. These Carrier 80s have issues this is my 3rd one and they all develop them over time it seems.

Certainly system sizing and duct work could be an issue, but if it were you'd have had that issue from day 1. Based on the amount of dust in the unit I doubt its brand new which means this is a recent problem. I find a lot of people close supply vents or damper down trunk lines which can cause the unit to trip on high limit as well.

Removed the front panel that is covering blower motor and it works now. Looks like it is not getting enough air from return. I guess I will leave it open

On the thermostat, I switched the blower to manual blowing and the blower didn't run. I jiggled the blower wires and it started blowing. After securing all blower plug wires, I retried it and all is well. So in my case, the burners fired, flame was detected ok, but after the 30 second heat-up period, I guess the burners overtemped and the overtemp switch sent a fault signal, which shut the heater down. This is my take on it anyway.

Your video helped me out. Thank you

I have Bryant furnace(3310AAV048110) installed 5.5 years, I get error 33. If I set my thermostat to 67 degrees it fails, if I leave it at 66 no issue. This was never a problem before. House is 100 years old, 3 returns all clear, 8 Air ducts, all open. Filter was clean, removed filter same issue. Tech came out and tried replacing flame sensor still same issue. He had to leave for another call. Can't get him out again. The first time I discovered this was Jan 27th and it was error 13. I think if you don't lower temperature to 66, it will keep trying and the error code goes from 33 to 13. Contractor said he opened a ticket with tech support(assume Bryant). I reschedule him and can't get him to keep his appointment. He did take readings for different sensors, all were good according to him.

I believe your real problem causing an over temperature trip was your vent pipe is undersized, looking at your video I see a 4 inch vent pipe all the way out. If you look at page 6 lines 2 of your installation manual it states to increase the hood vent exhaust immediately from 4 inches to 5 inches. This depends on model and btu input and length of run, and other appliances that are tied in. My furnace being 88,000 btu input required the 5 inch increase plus a 5.5 inch aluminized chimney vent.

Great video I'm having the same error code 33 however I have a Carrier furnace Model# 58STA/STX. Now first off I'm not at all familiar with anything related to a furnace. I've learned everything I know up to this point only in a few days. The Issue:My furnace is blowing cold air. WHen I took the panel off I noticed that I can hear the fan. I'm not getting any heat or activity from the glow stick I don't see any flames. I see that I'm getting 3 short flashes followed by 3 long flashes. The filter was dirty so I changed it and I've tried to do a manual reset. I pressed the Flame Rollout Switch and nothing happened. But it also says something about BVSS requires manual reset. I don't know where the BVSS is and how to reset it. All my vents are free and not restricted, I think I have proper vent sizing. Nothing has been changed or updated to the furnace since we moved here 3 years ago. I'm not sure how to go about checking the blower motor and capacitator and where it would be located. I'm sure that the furnace is getting adequate combustion air supply but I don't know what to look for if it's not.

Thanks for the video. Very helpful

I’m getting this error too. Should very first vent on the side the furnace be open? I always left it closed due to it being in the basement and it seemed like a waste a warm air since no one is down there.

quick tip... probably should have just checked to see if your centrifugal blower motor was wired at too low of a speed. (I'm assuming its a variable speed blower?) a quick switch of the wires and your blower is now pushing more CFM and that weird duct fix you did would'nt have been necessary(did that cost you money to make?) lol If you didn't have a variable speed blower than i'm completely wrong! :D

4 to 5 ton blower needs return air on both sides or from the bottom to supply enough air flow for that size furnace.

Thanks for the trouble shooting. It looks like air flow was this issue on mine as well, however a new less restrictive air filter did the trick. :S

I really hope this helps my mom!! She has no heat by the code 33 and i check the voltage of all parts and they all have proper voltage filter is new sensors are new control board is new... This is the only thing i haven't checked...

Take a gas pressure reading at the gas valve? Lower the gas pressure

I am getting 1 red blink, pause. Then 3 red faster blinks, please help, no heat

Thank you! What was the MERV rating on your filter. If it was high, did you try a lower restriction filter?

Thanks for a great video! Today I had the code 33 and 13 on a similar Bryant furnace called the heating ac co the tech said bad circuit board and had to replace the board though my furnace is only 6-7 yrs old! Cost of circuit board $ 570 !! Plus labor $ 195 close to $800 way too much. I am not tech savvy so had to believe the co tech!! Hope I was not "took"!

Had a dirt dobber nest in the flue vent on my 33' today.

Lonnie renda theres alit of thinng that can effect it iver heating if the furnace is reseting by itself sometimes the gas pressure is too much just have to clise it alittle bit more its too much gest that the blower cannot cool it down

This was very helpful! thanks :)

What do you need to cut a hole in the side like he did. I think he said just a jigsaw. Is that right?

Apparently I had filters I didn't know about. I cleaned them and presto!

Hello .. I have SAM COMMUNICATION FAULT 186 , so you know what that error supposed to be ??

Good explanation

had the same 33 code on a unit under the house,all switches were good and they never tripped,but had new on the truck,changed all and same code,unit wouldn't run long enough to get hot,flame rod good,filter good,no blocked vents,exhaust piping good,water column exact,after got it running,about to give up,pulled the thermostat,jumped it,ran perfect,30 min,still good,changed the thermostat and no codes for 3 months?why,shorted thermostat?another day in the life

I am having similar problem with a brand new furnace supplied by Bryant (two weeks new products). In the middle of heating, the thermostates will turn to black, out of picture. Then it turns on by itself. Tech came out and replaced with a new thermostates that was wired directionly to the circuit board by blower. It found out the same problem happened again. I do not know a code, but the light blinked three times short and then one time long. Can someone help me what error code will be?

Thanks so much for posting this. I did need to change my filter, which I did. Will the System Malfunction message go away once the furnace "figures out" the filter is clean? Or is there something I need to reset?

very helpful video thank you

What speed is your blower motor speed set at?

That really help thanks .

change motor speed to a higher setting

Whoever installed your furnace did not size the return correctly. It is NOT manufacturer defect. If you were to look into the installers instructions different size furnaces,( but input) require different cfm requirements. And unless you're a professional you shouldn't be tampering with equipment.

Thanks for the video just going over the different components helped me trouble shoot mine 👍

I am having the same problem with a different furnace. Tech came out and told me the same thing that you say in the video-- there is nothing we can do it is just getting too hot and tripping the sensor. He did his thing, reset the furnace (I guess some error codes needed to be cleared out which I don't know how to do) and then got it running. Cost about $315. We took out the filter and about 12 hours later, the same thing happened. I guess what I am getting at is can I just cut a hole in the side and install a duct on the side to get more air? I don't think I could run an entirely new return. Does it matter if I am just sucking air from the basement?

Nice video buddy

Help. Furnace runs eratically. I find by flipping the power switch off, then on again (The switch that's located on the side of heater unit). If that doesn't work. then I'll bang on the side of the heater by the power switch a few times and presto. It's running again for a few hours to a few days? Should I just replace the switch. Looks like a basic light switch.

I am also not even getting a flame or anything lighting but am getting the 1 slow light then 4 fast yellow lights

y that is just what should have been done from the start /this was great

I’m having the same problem. Wondering why this became a problem all of a sudden? The system is 12 years old. Subtle decrease in motor efficiency or slight buildup on heat exchanger?

Furnace doesnt shut off- New thermostat - Checked all wiring - Only way to turn it off is hitting the breaker?

Thanks Man

I've had the same code 33 problem for as long as I've lived in the house (7 yrs). Just had an HVAC guy here last week who said I needed a "box" installed below the blower so that it could get bottom and side air as return. Came back and raised up the entire furnace and put it on this "box". Charged me $1800, and now I STILL get code 33! But with the cover off, more air enters and it will run in heat mode forever. HVAC guy now wants to put a "bypass" on the system between supply and return to lower the static pressure. The video suggestion-- putting an auxiliary return intrigues me, although there is a water heater sitting on the opposite side of my furnace so that's not an option. I am tempted to just "try" a replacement sensor on the outside chance it is cutting out at too low a threshhold. Anyone have a part number ? This is a Carrier 58 STA/STX.

My problem with code #33 previously was indeed "excessive wind". Just happened again. How do I fix? (Wind conditions now normal).

I have a 33 error code then it added a 13 error code later. I thought it could be a dirty filter but after i installed a new one the error message persists, what should i do? The heating is working and i didn't notice any problems, but the message keeps showing up.

Help alot that was the problem

can you do a video for Error Code 14?

Not enough return air!

how did you wire the error code light to work on the outside of the funance?

My igniter Light Up 3 times then my gas heat starts y is that 34 is my code

Do not rely on that code, it can be the step before it that's causing the issue.Gas pressure being to high will do the same code 33, also if the fan is on the Blue wire it will cause not enough air to flow over the Heat Exchanger. I bet if I did a Static Air test on the furnace you would have a Very high Static Pressure excess of .7 which would cause the same code 33. Find a Great service company in your area and have them test Static Pressure, Gas Pressure and make sure your AC coil is clean as this will cause the same code...

This the exact thing that is happing to mine..

Pls help

Informative video ! I would suggest you pull fresh air from outside so you do not pull CO2 from the combustion air side into your house. You can run a 4 inch flex line from the side of your house to the return side. Thankyou. James Sasse. GodWhoisGod com

Tons of misinformation...Go to school.. but nice try..learn the concepts properly

Its not the design of the furnace,its the hack that installed it.also you have no business messing with a gas furnace son.lol

I have an old carrier furnace that blinks 3 times quickly then 3 times slower (3 ). ACCORDING TO the rear panel it is the roll over limit switch or lock out. I tried tsting then by-passing or jumping the switch to no avail as furnace blower just runs continuously. I did replace the unducer motor a year ago. I cleaned out the hvac, new filter, and did what I could. NOTE: The stages of this 80% carrier furnace are = (1) blower (2) inducer (3) ignitor, (4) then gas to burner on furnace, athat point it is supposed to start. ....My problem is that 3 - 3 code - Should i replace inducer motor again and the limit switch?