Furnace runs but produces very little heat; house does not warm up.

Safety first: Allow the furnace to cool before cleaning internal components.

Steps:

• 1. Check heat level setting: Ensure the control is not set to a low heat or economy mode. Increase the heat level and observe flame size.
• 2. Inspect hopper and fuel: Make sure fuel is feeding freely. Break up any bridging in the hopper and remove fines or sawdust that may restrict flow.
• 3. Clean heat exchanger: Use the built-in scraper rods (if equipped) and brush to clean the heat exchanger tubes. Vacuum accumulated ash from the exchanger area.
• 4. Verify combustion air: Check that the combustion air intake is not blocked and that the combustion blower is running at full speed.
• 5. Ductwork and filters: Ensure filters are clean and supply/return registers are open so heat can be distributed effectively.