Carrier 58SXB furnace error code 31

DonSz

I am getting an error code 31 "High Pressure Switch Fault" on my Carrier 58SXB furnace. It is running on natural gas. Previously, when I got this message I would clean the condensate lines and it would be fine. Now, the furnace gets the error and the condensate lines are clear. There are no blockages in either the intake or the vent lines. Thanks in advance for any suggestions.

beenthere

Try cleaning the trap.

DonSz

Thanks for the reply... I don't know how to clean the trap. The trap appears to be PVC or ABS plastic with a cap glued onto the bottom. I can't fnd any way to remove the cap. I took the lines off the top of it and blew my air compressor hose into it. Still no luck... I'm concerned that I might have a problem with the secondary heat exchanger and I don't know how to test if the problem is in there.

hvac benny

To clean the trap you need to remove all lines to it and run hot water through the open ports. I'm not familiar with this model, but this is how I clean the traps on other Carrier High Efficient models. If there is a buildup of reddish-brown "sludge" in the trap I would suspect the secondary heat exchanger is plugged, or soon to be plugged. In this case, pull the blower and look up inside the furnace, into the secondary HE. All you should see is metal. If you see any reddish-brown build up on the surface (sometimes it kind of looks like tiny worms coming through the surface) then your secondary HE is plugged AND rotted out. It could still be plugged even if you don't see this, it just means that the fins haven't eaten through yet. Going any further than just a visual inspection should be handled by a pro, as you really need to know what you are doing. Call Carrier, and they will most likely put you in contact with a company that knows what they are doing.

DonSz

Thanks for the reply. I'm going to have a pro come in and troubleshoot the problem. Thank you both for your time.