Control board displays Er1 and furnace will not start or feed pellets/coal.

Safety first: Turn the furnace OFF, unplug it from power, and allow it to cool completely before working near the exhaust or flue. Hot surfaces and live voltage can cause burns or shock.

Steps to check and correct:

• 1. Power reset: Unplug the furnace for 5 minutes, then plug back in and see if Er1 clears. If it returns, continue.
• 2. Locate the exhaust temperature sensor: On most US Stove furnaces, the exhaust temperature sensor (also called flue gas or stack temperature sensor) is mounted on the exhaust housing or flue outlet with two small screws and a two-wire harness.
• 3. Inspect wiring and connector: Check the sensor wires from the sensor to the control board for cuts, melted insulation, or pinched spots. Reseat the connector at both the sensor and the control board. Look for corrosion on the terminals.
• 4. Test the sensor (if you have a meter): With the unit unplugged, disconnect the sensor and measure resistance across the sensor leads. Compare to the value in the US Stove service manual for your model at room temperature. An open circuit (infinite resistance) or a dead short (near 0 ohms) indicates a bad sensor.
• 5. Clean the exhaust path: Excessive soot or ash buildup can overheat or damage the sensor. Remove the flue pipe (when cool) and clean the exhaust blower housing, flue passages, and vent pipe per the manual.
• 6. Replace the sensor if defective: Remove the mounting screws, pull out the sensor, install the new US Stove exhaust temperature sensor with the same orientation, and reconnect the harness firmly.
• 7. If Er1 persists: After replacing the sensor and verifying wiring, the fault may be in the control board input circuit. At this point, contact a qualified technician or US Stove support before replacing the control board.