Furnace won't ignite / no heat
Ranked from 3,800 repairs on furnaces with this symptom. Narrow it below and the ranking recomputes — the more you can tell us about what your furnace is actually doing, the shorter this list gets.
Before you start — Kill the power before you touch anything gas · electrical safety
Switch the furnace off at the service switch AND at the breaker — they are not the same thing, and the blower can start on its own while your hands are in the cabinet. The parts ranked below are safe DIY swaps with the power off. Gas valve and heat-exchanger work is licensed-tech territory in most jurisdictions.
If you smell gas: stop. Don't switch anything on or off, don't use your phone indoors. Leave the building and call your gas utility from outside.
Narrow it down
My furnace igniter never glows — what's wrong?
An igniter that never glows has usually failed open: about 74% of these repairs end with a new hot surface igniter. Pull the igniter and check it for continuity with a multimeter — an open circuit confirms it. If the igniter reads good, suspect the control board (12%) or a pressure switch stuck open (9%), either of which stops the board ever calling for ignition.
-
Most likely — 74%
IGN-271W
Universal Hot Surface Igniter Kit
67 in stock · ships today
$34.95 Pro price $29.71 save $5.24 (15%)74% of matching repairsNo glow at all is the igniter's signature failure — the element has cracked and gone open circuit. It is also visible: look for a hairline crack across the ceramic.
Try this first: Confirm before you buy: continuity across the igniter leads. Open circuit = failed.
-
Also check — 12%
CTB-1084
Integrated Furnace Control Board
23 in stock · ships today
$128.00 Pro price $108.80 save $19.20 (15%)12% of matching repairsIf the igniter tests good and still never energises, the board is not sending it 120V — check for voltage at the igniter plug during a call for heat before condemning the board.
-
Less likely — 9%9% of matching repairs
A pressure switch stuck open stops the sequence before ignition, so nothing ever glows and the inducer just runs.
The remaining 5% of matching repairs resolved without a replacement part — a filter, a reset or a thermostat setting.
Verify against your model
We ranked these from the symptom. Your model number turns a ranking into a verdict.
Where's my model number? (photo guide)Not sure? Talk to a tech
Send a photo of your rating plate and a real tech confirms the part before you buy it. Free, about 10 minutes.
Ask a tech — free