1 blink
Soft lockout
This code typically points to
- No flame sensed after four ignition trials
- Four flame failures during one call for heat
Next checks to confirm
- Verify gas supply and manifold pressure
- Verify polarity and grounding
- Inspect spark/ignitor alignment
- Inspect flame sensor and flame carryover
- Verify gas valve wiring and 24V at valve during trials
Escalation
System attempts ignition 4 times, then enters 1-hour soft lockout; main blower and inducer run 180 seconds between 2nd and 3rd trials; neither ignition control nor gas valve re-energizes until lockout expires or is reset
Reset behavior
Turn off 115V power to furnace OR turn thermostat OFF for 5-10 seconds.
Urgent
Fix now