Dettson furnace displays E17; unit may shut down during operation on very cold days.

Safety first: Turn off power before working around water and electrical components.

• 1. Locate condensate trap and drain: On condensing Dettson furnaces, a plastic trap and tubing carry condensate to a drain or pump.
• 2. Inspect for clogs: Remove the trap if possible and flush it with warm water to clear debris or slime. Use a small brush if needed.
• 3. Check drain line routing: Ensure the tubing slopes continuously downward with no sags that can hold water and freeze.
• 4. Test condensate pump (if present): Pour water into the pump reservoir and verify it activates and discharges water. Replace the pump if it does not run or fails to pump.
• 5. Insulate or relocate drain (cold climates): If the drain line runs through unconditioned space, insulate it or reroute to prevent freezing.
• 6. Reset and test: After clearing the drain, restore power and run the furnace. Confirm E17 does not return.