Replace a Hot Surface Igniter (Furnace)

Match the OEM igniter and voltage type (120 V silicon-carbide vs newer line/low-voltage silicon-nitride), handle the element by its ceramic base ONLY (oil + bumps crack carbide), set the gap/position per spec, verify cold resistance (SiC ~40–90 Ω), then confirm it glows and lights the burners.

Approx. 45 min

Before you start

•Igniter confirmed as the fault: cracked/broken element, no glow on a call (with 120 V present), or open/out-of-range cold resistance on the meter — not a board or pressure-switch problem upstream.
•Correct REPLACEMENT igniter: match the OEM part and the voltage type — older furnaces use 120 V silicon-carbide; many newer ones use a robust silicon-nitride element (often line- or low-voltage) that is NOT interchangeable.
•Power can be killed at the furnace switch/breaker and the gas left off until light-off verification.

Tools & materials

Multimeter (cold resistance of the element) · Nut drivers/screwdrivers · Replacement OEM igniter + gasket if used · Clean gloves / handle by base only

View

0% complete

Isolate & remove

Kill power and gas, verify dead
Turn off the furnace switch and breaker and shut the manual gas valve. Verify 0 V at the igniter leads before disconnecting — the igniter sees 120 V (or line voltage) during the trial-for-ignition.
Tools: Multimeter
⚠ Verify 0 V — the HSI is energized on the ignition sequence; a hot element also causes burns.
Unplug and remove the old igniter
Disconnect the igniter plug/leads, remove the mounting screw(s), and withdraw the element from the burner assembly. Note its exact position and gasket so the new one seats identically.
Target: Note position, depth, and gasket orientation before removal

Install the new igniter

Handle the new element by its base only
Hold the silicon-carbide/nitride element by the ceramic base — never touch the glow element with bare skin or bump it. Skin oil and microcracks cause early failure; clean any accidental touch with alcohol.
⚠ Never touch the element body; oil and impact crack the carbide and cause premature failure.
Mount and set the gap/position per spec
Seat the igniter with its gasket and set the position so the element sits in the burner flame path at the OEM gap/insertion depth. Too far out won't ignite reliably; too deep overheats and cracks it.
Target: Element positioned in the burner per OEM gap/insertion depth; gasket sealed
Verify cold resistance
Before energizing, ohm the element cold. A silicon-carbide HSI typically reads ~40–90 Ω cold (silicon-nitride differs — use the spec). Open or wildly out-of-range = a bad element or bad plug.
Tools: Multimeter
Target: SiC element ~40–90 Ω cold; out-of-range or open = replace/recheck

Verify glow & light-off

Restore power and confirm it glows
Restore power (gas still off), call for heat, and watch the trial-for-ignition: the element should glow bright orange/white within the warm-up time. No glow = check 120 V at the leads and the board's igniter output.
Target: Bright, even glow during trial-for-ignition
Open gas and confirm burner light-off
Open the gas, run a full cycle, and confirm the burners light promptly from the glowing igniter and that flame sense holds (no flame-loss lockout). Watch a couple of cycles for reliable carryover.
Target: Burners light promptly and stay lit; no ignition lockout