Igniter
Hot surface and spark igniters.
Furnace Blowing Cold Air: A Diagnostic Order That Finds It Fast
Why a gas furnace blows cold or lukewarm air, in the order to check it: thermostat fan setting, lockouts, flame proving, limits, gas supply, and duct leaks.
How to Test a Furnace Hot Surface Igniter (and Why They Keep Failing)
How to test a hot surface igniter by watching the sequence, checking voltage and measuring resistance, the difference between silicon carbide and silicon nitride igniters, and what shortens their life.
Furnace Ignition Lockout: Failed Ignition Troubleshooting Step by Step
Diagnose a furnace that tries to light and locks out by following the ignition sequence: inducer, pressure switch, igniter, gas valve, flame sense.