Furnace inducer runs but burners never light
The small blower at the top of the furnace spins up and keeps running, but the igniter never glows and the burners never light. The furnace is waiting for a signal that never comes.
What is actually happening
The inducer starts first in every heating sequence. Before the control will go any further, it has to see the pressure switch close — a diaphragm switch connected by a small hose to the inducer housing, which closes when the inducer generates enough suction. That switch is what proves the flue is clear and the inducer is actually moving air. Until it closes, the control will not energise the igniter, and it will certainly not open the gas valve.
What causes it
In cold weather the most common cause is a blocked intake or exhaust termination outside — snow, ice, a bird's nest, or a plastic cap left on. Then: water in the pressure switch hose or in the condensate trap, a cracked, kinked or disconnected hose, a blocked condensate drain backing water into the collector box, a failing inducer that spins but does not develop enough suction, or a failed switch. An inducer that hums, spins slowly, or has a bearing noise will look alive and still not close the switch.
The codes that report this
18 codes across 9 control families. Each links to what that manufacturer says about it.
| Brand | Code | What it reports |
|---|---|---|
| Armstrong | 10 flashes | Watchguard — pressure switch opened five times during one heat demand |
| Armstrong | 9 flashes | Pressure switch failed to close, or opened during a heat demand |
| Carrier | Status code 31 | Pressure switch did not close, or reopened |
| Goodman | 3 flashes | Pressure switch will not close |
| Goodman | 9 flashes | High stage pressure switch stuck open |
| Goodman | E2 | Low stage pressure switch stuck open |
| Goodman | E9 | High stage pressure switch stuck open |
| Goodman | 3 double red flashes | Second stage pressure switch stuck open, or an inducer error |
| Goodman | 3 red flashes | First stage pressure switch stuck open, or an inducer error |
| Heil | 3 flashes | Low pressure switch still open 30 seconds after the inducer started |
| Heil | 9 flashes | High pressure switch open when it should be closed |
| Lennox | Alert code 223 | Low pressure switch open |
| Lennox | Alert code 227 | Low pressure switch open in run mode |
| Lennox | Alert code 271 | Low pressure switch open — Watchguard |
| Lennox | Alert code 272 | Low pressure switch open in run mode — Watchguard |
| Rheem | 2 blinks | Pressure switch did not close within 10 seconds |
| York | 3 double red flashes | Second stage pressure switch stuck open |
| York | 3 red flashes | Pressure switch open, or first stage pressure switch open |
Worth knowing
This is the furnace correctly refusing to burn gas because it cannot prove the flue is clear. Jumpering the pressure switch to force it to run defeats the interlock that stops combustion products entering the house.
Other symptoms
- Lights, then shuts off after a few seconds
- Igniter glows but the burners never light
- Nothing at all, no lights on the control board
- Runs for a while, then trips on high limit
- Runs briefly, stops, starts again, then quits
Sources
- Allied Air Enterprises — A80UH1E and 80G1UHE Installation Instructions 507330-03, Table 7: Diagnostic Codes for -02 Control
- Carrier 58MCB Service Manual, 327884-101 Rev. B — status codes
- Goodman Manufacturing — Diagnostic Code Identification System (model-specific fault code lookup)
- International Comfort Products *9MPT and *9MPV installation instructions — Gas Valve Diagnostic Codes (third-party archive of the ICP document)
- Lennox Residential Communicating Systems Alert Code Guide, document 100017, March 2023 — Table 2, Alert Codes and Troubleshooting
- Rheem Gas Furnaces Installation Instructions 708503a — *RC 92+ Full Size Upflow and *RL 90+ Full Size Downflow Condensing Furnaces, Sequence of Operation
- Johnson Controls Unitary Products technical service letter ST-045-09 — York UTEC furnace boards, fault code tables and retrieval procedure