Heil furnace LED shows code 31; inducer may run but pressure switch does not close, or furnace shuts down on pressure fault.

Safety: Turn off power and gas before working on venting or condensate lines.

Steps to check:

• Inspect vent and intake: Check outside terminations for obstructions (ice, snow, nests). Clear any blockage and ensure proper clearances per Heil installation manual.
• Check condensate drain: For condensing Heil furnaces, inspect the condensate trap and hoses for clogs or kinks. Flush the trap with warm water and reassemble.
• Examine inducer housing: Look for water accumulation in the inducer assembly. A blocked drain can cause water to back up and affect pressure.
• Test pressure switch tubing: Remove and clear tubing, then reattach securely.

When to call a pro: If the pressure switch still does not close with clear venting and drains, a technician should measure draft pressure, verify correct switch rating, and replace the inducer or pressure switch as needed.