If a hot surface igniter is open, what would it read on an ohmmeter?

When a hot surface igniter is open, it means the electrical pathway through the igniter has been broken, preventing current from flowing. An open circuit will show infinite resistance when measured with an ohmmeter. This condition indicates that there is no continuity through the igniter.

In practical terms, if an ohmmeter is used to check an open hot surface igniter, the reading will display as infinity ohms or "OL" (over limit) on many multimeters. This reading signifies to the technician that the igniter is faulty and needs to be replaced, as it should have a specific resistance value when functioning correctly.

Understanding this concept is crucial in HVAC troubleshooting, as an open igniter indicates that the furnace or heating appliance won't ignite due to the lack of heat produced by the igniter.