Furnace LED shows code 31; inducer may run but burners do not light, or unit shuts down mid-cycle.

Safety first: Shut off power before working inside the furnace. Do not modify or bypass the pressure switch.

• Check venting system: Inspect the entire length of PVC vent and intake (if applicable) for sags holding water, separations, or blockages. Correct any low spots and clear obstructions.
• Clean condensate trap: On condensing Bryant furnaces, remove the condensate trap, flush it with warm water, and clear any debris. Reassemble and ensure hoses slope toward the drain.
• Inspect pressure tubing and ports: Remove the tubing from the inducer and pressure switch. Use a small drill bit or paperclip by hand to gently clear the inducer port. Do not enlarge the hole.
• Verify combustion air: For sealed-combustion models, ensure the intake termination is not blocked and that the furnace room has adequate ventilation if using indoor air.

If code 31 persists after cleaning and vent checks, the pressure switch or inducer assembly may be out of specification and should be tested and replaced by a technician.