Hi, I'm not a tech, but good at troubleshooting, I hope. I have a Bryant HVAC unit that was installed a year ago and I'm having problems with the heater shutting off. the heater shuts off and gives an error code 33, I have narrowed it down to the point that I can make the problem happen by running the unit with the service door on. If I take the door off, everything runs as it should. I then metered the limit switches and one of them is getting triggered, causing the error code. My question is, can the unit have two different part numbers for the limit switches? the one that is getting triggered is part number HH18HA607A, but the other one is not getting triggered and its part number is HH18H515A. I do not know if the problem is because there is not enough airflow and that is what causing the LS to open or if it's a faulty LS. Please, any suggestions are appreciated. The HVAC model is 800SA60110E21A
Thank you
I believe the LS opens at 180F, so I would measure the temperature behind the limit and see if it's tripping sooner.
It does sound like an airflow issue though. Is there a hidden filter or AC coil that may be plugged or maybe lack of return air?
Is this a 2 stage furnace? You can also measure the temperature in the supply and return air ducts to check the temperature rise versus what the rating plate on the furnace says.
Almost guaranteed air flow issue, check your filter, if you replaced your old filter with a high MERVA 3M filter , that will cause huge issues in static pressure. Otherwise , you might also have a return opening blocked.