Alarm 56 or 66 — Combustion air inducer switch not sensed as closed

What does Alarm 56 or 66 mean?

These alarms are triggered if the S18 or S45 switches are not detected as closed within 30 seconds after the combustion air inducer starts. They can also trigger if these switches are sensed as open for three seconds while the unit is trying to heat.

• S18 or S45 switches are not closing properly.
• Issue with the combustion air inducer.
• Wiring problem with the S18 or S45 switches.
• The switches are open for too long during a heating demand.

Click steps to track your progress.

1. 1

   Verify that the S18 and S45 switches are functioning correctly.

2. 2

   Check the wiring connections for the S18 and S45 switches.

3. 3

   Ensure the combustion air inducer is operating as expected.

4. 4

   Review parameter settings related to switch monitoring if applicable.