Display shows Er5 and the furnace stops feeding fuel; combustion blower may continue to run for cool-down.

Safety first: Turn off power and allow the furnace to cool. Exhaust components can be very hot. Never operate the unit with safety switches bypassed.

Steps:

• 1. Check doors and gaskets: Ensure the firebox door, ash pan door, and any clean-out doors are fully closed and latched. Inspect gaskets for damage or gaps that could reduce vacuum.
• 2. Inspect the venting system: Remove the vent cap and check for bird nests, ash buildup, or obstructions. Clean the vent pipe per the manual, including elbows and tees.
• 3. Locate the vacuum switch: Typically a round or rectangular device with two electrical terminals and a small rubber or silicone hose connected to the firebox or exhaust housing.
• 4. Check the vacuum hose: Inspect for cracks, holes, or disconnections. Remove the hose and blow through it to ensure it is clear. Clean any ash from the hose barb on the stove.
• 5. Test the combustion blower: With the unit running (if possible), verify that the combustion blower starts promptly and runs at full speed. Listen for grinding or squealing. A weak blower may not create enough draft to close the vacuum switch.
• 6. Test/replace the vacuum switch: With power off, disconnect the wires and hose. Gently blow into the switch while checking continuity across the terminals (using a meter). If it does not close at all, replace it with the correct US Stove vacuum switch.
• 7. Restart and monitor: After cleaning and replacing any faulty parts, restart the furnace. If Er5 returns, stop using the unit and have a professional check for installation or chimney sizing issues.