If you’ve been quoted an igniter replacement on your Lennox furnace, the price is almost certainly fair, and the diagnosis is usually right. A failed igniter is the single most common reason a Lennox G61 or SLP98 series furnace won’t light, and it’s a straightforward repair when a tech knows what they’re doing.
Why igniters fail (and how fast it happens)
The igniter is a small silicon nitride or silicon carbide element that glows white-hot to light the burners. It’s fragile by design. Most Lennox igniters are rated for several years of regular use, though I’ve seen them go in 18 months on a system that cycles heavily, and I’ve seen originals last 12 years on a unit in a mild climate.
The main failure modes: the element cracks (usually from thermal stress or being touched during a prior service), it develops a hairline fracture you can’t see with the naked eye, or the resistance drifts out of spec and it stops drawing enough current to glow reliably. On SLP98-series furnaces especially, a weak igniter will often cause intermittent no-heat, where the furnace tries to light, fails, retries a couple times, then locks out. That lockout behavior is what usually sends homeowners to Google.
Oil from bare hands during a previous repair can also shorten igniter life significantly. It’s not always the tech’s fault, but it matters.
How a tech confirms the igniter is the problem
A thorough tech won’t just eyeball the igniter and swap it. Here’s what a real diagnosis looks like.
First, pull error codes from the control board. Lennox boards store fault history, and a lockout code pointing to ignition failure is meaningful context. It doesn’t prove the igniter is bad, but it narrows the field fast.
Second, measure igniter resistance with a multimeter. Silicon nitride igniters (the white, rectangular type on most modern Lennox furnaces) have a resistance range that varies by model, so a tech should check the service manual for the specific spec. What’s definitive is an OL (open/infinite resistance) reading, which means the element is cracked through. A borderline reading tells you it’ll probably fail again soon even if it lights today. Silicon carbide igniters (older, dark gray, brittle) measure lower resistance and are less forgiving of out-of-spec readings.
Third, watch the igniter glow on a test call. If it glows but the burner won’t light, the gas valve, pressure switches, or inducer may be the actual issue. A misdiagnosed igniter replacement that doesn’t fix anything is frustrating and avoidable.
Fourth, check the 120V supply to the igniter during the ignition trial. No voltage means the control board isn’t firing the igniter, which points upstream to a pressure switch, draft inducer, or board itself.
If your tech did these steps, you can feel good about the diagnosis. If they just looked at it and said “yep, igniter,” ask them to pull the fault codes at minimum.
Lennox igniter part numbers
Lennox uses different igniters across their product lines, and the part number matters. The wrong igniter can have the wrong resistance range and cause nuisance lockouts even when installed correctly.
For the G61 series, the standard OEM igniter is the 19W61 (also listed as LB-112237A), a 95V silicon nitride assembly. For the SLP98, Lennox’s own night service kit uses the 70W16 (LB-112237B), a 120V assembly. These are the part numbers that show up in the LennoxPros catalog and major supply houses.
Your tech should pull the model and serial off the furnace nameplate and confirm the correct part before ordering. Aftermarket igniters exist and many work fine, but on a modulating furnace like the SLP98, OEM is worth the extra cost. The resistance spec is tighter, and the communicating board is less forgiving of variations.
What the repair involves
Getting to the igniter on a G61 or SLP98 requires working inside the burner compartment — accessing gas components, handling a fragile element that can’t be touched with bare hands, and verifying the correct voltage supply before and after. An experienced tech does this in 30 to 45 minutes and tests the furnace before leaving. The parts are inexpensive; the value is in doing the diagnosis right first so you’re not buying parts that don’t fix the problem.
Things that can add time: corroded fasteners, a heat-soaked harness connector, or finding a secondary issue alongside the bad igniter. Budget an hour for the full call and you won’t be surprised. If the igniter isn’t the only issue, a tech will catch it during the same visit rather than you starting over after a part swap that didn’t help.
Cost: what’s reasonable
Part plus labor on an igniter replacement generally runs somewhere in the $150 to $350 range across the Bay Area, depending on the company, whether it’s after-hours, and what part they stock. OEM Lennox igniters cost more than aftermarket. That range is publicly available knowledge and aligns with what I see in the field. If someone quotes you $400 or more for a standard igniter swap with no other parts involved, ask for an itemized breakdown. If someone quotes you $89 flat, ask what igniter they’re installing.
Get the quote in writing before the work starts. Any honest shop will give you one.
Get it diagnosed, then get it fixed
A furnace that won’t light is not the time to guess. Skipping the resistance measurement and voltage check before swapping the igniter is how homeowners buy a part, install it, and still have no heat because the real problem was a pressure switch or a failing board. The igniter’s the most common culprit, but it’s not the only one.
If you’re in the Tri-Valley or East Bay, call us. We’ll confirm the diagnosis, give you a written quote, and get it running same or next day in most cases. adriumservice.com.