Bryant 315AAV Error Code 12: Blower On After Power Up
What Does Code 12 Mean?
Status code 12 on the Bryant 315AAV is a 'blower on after power up' notice. If line power returns while the thermostat is already calling for heat — the R to W/W1 circuit closed, or an F/G/Y signal present — the control runs the variable-speed blower for about 90 seconds during the blower on-delay period. This is a designed response, not a fault.
The behavior exists so the furnace handles a power interruption gracefully. When electricity comes back after an outage or after the breaker is cycled, the control briefly runs the circulating blower to settle the system before resuming its normal sequence. On this variable-speed control, that momentary run is logged as code 12.
Because it is tied to a heat call existing at the instant of power-up, code 12 typically appears right after an outage, after resetting the furnace breaker, or after toggling the furnace power switch. Once the 90-second period ends, the furnace continues its normal heating sequence, and the code carries no required action.
What You'll Notice
- The blower runs for roughly 90 seconds right after power is restored to the furnace
- The air from the vents may feel cool at first, then normal once the burners complete startup
- The event follows a power outage, a breaker reset, or the furnace switch being turned back on
How This Is Diagnosed
Code 12 is understood by context rather than diagnosed as a fault: it corresponds to power returning while a heat call was active. Confirming that a power interruption or reset just occurred, and that the furnace then proceeds into a normal heating cycle after the brief blower run, is enough to conclude no repair is needed.
- The blower runs continuously and never stops after the initial 90-second startup period
- The furnace repeatedly loses power on its own, forcing frequent code-12 restarts, which points to an underlying power problem
Frequently Asked Questions
Why did my Bryant 315AAV blower kick on by itself after the power came back?
Because the thermostat was calling for heat when power was restored, the control runs the blower for about 90 seconds as normal startup behavior, logged as code 12.
Do I need to reset anything after code 12?
No. Once the short blower run finishes, the furnace resumes its normal heating sequence on its own. No action is required.
Sources
✓ Verified against manufacturer service manual — March 2026