Lennox furnace Alert code 207: Hot surface igniter sensed open
Alert 207 means the hot surface igniter circuit is open. Lennox's guidance is to measure the igniter's resistance and replace it if it falls outside the range in the furnace installation instructions.
Applies to: Lennox communicating gas furnaces on systems using the S30, S40 or comparable communicating thermostats, as documented in the Lennox Residential Communicating Systems Alert Code Guide.
What it means
A hot surface igniter is a ceramic element that glows red hot to light the gas. It fails by cracking, and a cracked igniter is electrically open — which is exactly what this alert reports. What makes Lennox's guidance useful is its specificity: measure the resistance and compare it against the range published in that furnace's own installation instructions. That converts a judgement call into a measurement, and it means the correct range depends on the model rather than being universal. An igniter that reads open is failed by definition; one that reads out of range is failing.
Most common causes
- A cracked or failed hot surface igniter, which is the usual cause.
- The igniter wiring disconnected, loose, or damaged.
- A connector at the igniter not seated.
- An igniter at the end of its service life, since these are consumable parts.
- Damage during previous service work, since igniters are fragile.
How to diagnose it
- Note whether the igniter glows at all during a start attempt, if the furnace has a sight glass. An igniter that never glows fits this alert.
- Note whether the furnace has been serviced recently, since igniters break easily when handled.
- Note the age of the furnace and when the igniter was last replaced, since these are wear parts.
- Do not attempt to measure the igniter yourself — it is inside the burner compartment.
How to fix it
- This is technician work in the burner compartment and ignition circuit.
- Ask the technician to measure resistance against the range in that furnace's installation instructions, as Lennox specifies, rather than replacing on suspicion.
- A replacement igniter should be the correct part for the model, since resistance ranges differ.
- Handle expectations on cost: an igniter is one of the more affordable furnace repairs and one of the more common.
Notes
Hot surface igniters are consumable. They fail eventually on every furnace that uses one, and a furnace more than a decade old that has never had one replaced is due. This alert is often the furnace reaching an ordinary maintenance point rather than developing a fault.
Related
All codes for this manufacturer
Lennox furnace alert codes — every code, with what differs between models.
What the fix costs
This is one of the most predictable repair bills in heating: the ignitor cost guide puts a hot surface ignitor at $150–350 installed on a standard visit, $250–500 after hours, with the part itself $20–60 for a universal silicon nitride element or $40–120 for brand OEM. The spread between part and installed price is the truck, the confirming diagnosis, and the warranty — and on alert 207 the confirming diagnosis is short, because the control has already reported the circuit open. Igniters are also wear parts on a clock (three to seven heating seasons is a normal life), so an open igniter on an older furnace is routine aging, not a symptom of something larger.
DIY or call a pro
The ignitor cost guide makes the honest DIY case — on many furnaces the element is two screws and a plug behind the burner door — and the honest limits apply doubly when a code is involved: the resistance measurement Lennox specifies, against the range in the model's own installation instructions, is meter work that decides whether the igniter is actually failed or the fault is in its supply. If you do proceed with a like-for-like swap: power off at the furnace switch first, never touch the new element's ceramic with bare fingers (skin oil creates the hot spots that crack it), and the moment access requires disturbing any gas piping, stop and call — that is the line. If the new igniter dies quickly or reads fine but the alert persists, stop guessing; the triggering circuit is implicated, and that is alert 290 territory.
The same fault on other brands
Lennox reporting “igniter sensed open” as its own code is a diagnostic gift not every brand gives. York's 12 red flashes matches it (open hot surface ignitor), but Goodman, Trane and York's older tables famously pair a failed igniter with a bad earth ground in a single code — Goodman's 8 flashes is the canonical example — because those controls cannot tell the two apart. The igniter codes hub maps which brands separate the faults and which conflate them.
What this looks like
From the outside, this usually shows up as the furnace turns over but never lights — that walkthrough covers what to check in order, and when it stops being a homeowner job.