Carrier 58MVP Error Code 12: Blower On After Power Up
What Does Code 12 Mean?
Status code 12 on the Carrier 58MVP indicates that the blower motor activated for approximately 90 seconds after power was restored to the furnace. This happens specifically when the furnace powers up while the thermostat is actively calling for heat (the R-W/W1 circuit is closed), or when that circuit opens during the blower on-delay period.
This is a built-in safety feature, not a fault condition. When power is restored during a heating call, the furnace runs the blower briefly to clear any residual heat from the heat exchanger before starting a fresh ignition cycle. This protects the heat exchanger from thermal stress and ensures safe operation.
You might see this code after a power outage that occurred while the furnace was running, or after manually cycling the furnace power switch during a heating call. Once the 90-second blower run completes, the furnace will resume normal operation and respond to the next thermostat call as usual.
- If the blower continues running indefinitely beyond the 90-second period, which could indicate a relay or control board issue
✓ Verified against manufacturer service manual — March 2026