Dettson furnace will not start; control board shows E1 and the inducer motor never comes on.

Safety first: Turn off power to the furnace at the service switch or breaker and shut off gas before removing panels. Allow the furnace to cool.

• 1. Inspect intake and exhaust pipes: From the furnace to the outside termination, check PVC vent and intake pipes for ice, leaves, bird nests, or debris. Clear any blockage and ensure terminations are not buried in snow.
• 2. Check pressure switch tubing: Remove the front panel, locate the pressure switch on the inducer housing. Inspect the silicone tubing for cracks, kinks, water, or loose connections. Re-seat both ends firmly and replace tubing if brittle.
• 3. Test pressure switch operation: With power restored and thermostat calling for heat, listen for the inducer to start. Once running, the pressure switch should click closed. If the inducer runs but the switch does not close, the switch may be defective or the inducer is weak.
• 4. Verify condensate drainage (condensing models): If your Dettson furnace is a condensing model, check the condensate trap and drain line for clogs that can flood the inducer housing and affect pressure. Clean the trap and flush the drain line.
• 5. Replace pressure switch if needed: If tubing and venting are clear and the inducer is operating but E1 persists, replace the pressure switch with the correct Dettson-rated part. Label and transfer wires one at a time.
• 6. Reset and test: Restore power and gas, then call for heat. Confirm the inducer starts, E1 clears, and the burner ignites normally.