Bryant Furnace Code 31 [Fixed]

If you are dealing with Bryant furnace code 31, then this is a perfect guide for you. In this troubleshoot shooting guide, we’ll walk you through the common causes for a Bryant furnace status code 31 and how to troubleshoot and fix the problem behind this code.

Bryant furnace code 31 indicates that the pressure switch did not open or has reopened during operations.  The causes for this problem can range from obstructed or disconnected pressure tubes, restricted vent, detective inducer motor or a defective  pressure switch.

Lets look at the following chart that shows the possible causes for this error coded and the solutions.

Read also: Bryant Furnace Code 33 [Solved]

Updated: Another known issue that will trigger code 31 on your Bryant Furnace is a blocked condensate drain line. Ensure its unlocked and clear. Will update on this issue in due course.

Possible causes for Bryant Furnace Code 31

Possible causeFix
Defective pressure SwitchTest pressure switch/ replace if necessary
Obstructed pressure tubingsCheck obstructed vac tubings
Defective inducer motorReplace inducer motor
Blocked exhaust ventCheck for blockage in the exhaust vent 
Defective furnace control boardReplace furnace control board

Defective pressure switch

A Bryant furnace code 31(“open pressure switch”) could also be triggered by a defective pressure switch.

 This switch ensures there’s proper airflow for safe combustion. If the pressure switch is defective or stuck open, it can sense and give  false or unexpected pressure.. 

This can  trigger error code 31, as the furnace’s control board interprets this as a potential safety risk, preventing the furnace from starting. 

The control board may believe  there’s inadequate airflow, safeguarding against hazardous combustion conditions.

Read also: Carrier Furnace Code 31 [Solved]

Obstructed pressure tubings

Ensure the tubings connecting the pressure switches are not is not kinked, deteriorated or doesn’t have water in it. 

Many times you may also have clogged ports (where vacuum tubings attach the switch.). You can  poke a paperclip into the port where the tubing connects but not into the switch connection )

 This sometimes does the trick.

Defective inducer motor

The inducer motor is responsible for creating the draft that pulls air through the combustion chamber and exhaust gases out of the venting system.

 If the inducer motor is malfunctioning or not running at the correct speed,  it won’t do this job and can cause the pressure switch to reopen or not close and that can  trigger a code 31 error.

If you have a bad inducer motor, you’ll have to get a replacement to fix the problem

Defective pressure switch

Start by testing if the pressure switch is defective.

Turn off the furnace for about 5 minutes then turn it on

After the fan starts running remove one of the leads from the pressure switch and connect it to the other lead. 

 If the sequence continues then you may have a faulty pressure switch or possibly a weak fan. 

The next thing you would check is the actual  draft pressure on the exhaust. But this step will need a manometer and they can be expensive. 

Replacing the switch is the way to go in this  case since it’s less money than a manometer (or a new draft fan) and it is a likely culprit.

Blocked exhaust vent

A blocked exhaust vent can cause a furnace pressure switch to remain open because the blockage prevents the inducer fan from creating negative pressure. 

The pressure switch senses that the negative pressure amount is off and turns on, which closes the circuit and shuts the furnace down.

 If the exhaust flue is blocked, the pressure switch won’t close that would trigger status code 33.

Sometimes snow can block the exhaust vent. Check the exhaust for any blockage and clear it where necessary.

Defective furnace control

A furnace control board is more like  the central command system for managing various components of a furnace’s operation. It regulates processes such as ignition, temperature control, and safety mechanisms.

If the control board malfunctions, it can erroneously interpret the pressure switch as open when it is not, disrupting the furnace’s ignition sequence. This triggers the code 31 error, even though the pressure switch may be functioning correctly.

If you think you have a bad furnace control board, the only way to fix this problem is to get a replacement.

Final thought

In closing, whenever you have a Bryant furnace code 31 flash, always remember that this code has something to do with the pressure switch not closing or reopening. 

Otherwise I hope you have successfully  fixed  this code. If you haven’t found the underlying problem behind this status code, it’s perhaps a great idea to call a local pro to come onsite.

Thanks for reading.

See also: Bryant Furnace manual

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