Furnace displays E11; inducer runs continuously without ignition attempts

Safety first: Turn off power before testing or replacing the pressure switch.

• Check tubing routing: Verify that the pressure switch tubing is connected exactly as shown on the Napoleon furnace schematic. Incorrect connections can hold the switch closed.
• Test switch at rest: With power off and tubing removed, disconnect one wire from the pressure switch and test continuity across the terminals. At rest (no suction), the switch should be open (no continuity). If it reads closed, the switch is stuck and must be replaced.
• Inspect for moisture: Look for water in the pressure tubing or switch. Condensate backup can flood the switch. Clear the condensate system if water is present.
• When to replace: Install a new Napoleon-specified pressure switch if the old one is stuck closed or contaminated. If a new switch behaves the same, the control board may be misinterpreting the signal and require replacement.