Furnace attempts to start but stops; status LED shows code 12 (blower on after power-up).

Safety first: Do not remove panels with power on. Turn off power at the breaker or service switch before touching internal components.

Code 12 on many Bryant furnaces is informational and indicates the blower is running after power-up, often to clear residual heat:

• Wait 3–5 minutes: Allow the blower to complete its timed run. The code should clear and the furnace should respond to a new heat call.
• Check thermostat call: Confirm the thermostat is calling for heat. If not, the blower may simply be in a post-purge mode.
• Inspect for overheating signs: If the blower runs continuously and the furnace is hot to the touch, a previous high-limit trip may have occurred. Check supply and return vents for blockages and ensure filters are clean.

If the blower never shuts off and code 12 persists with no heat, there may be a stuck relay on the control board or a wiring issue.