Blower on after power-up. The blower runs for 90 seconds if the furnace is powered up during a call for heat, or if that call opens during the blower on-delay. The same guide's sequence says the amber LED flashes 12 during those 90 seconds, then stays on continuously if no fault is found.
Bryant 12 on the TG-GFB80-02 chart is the blower running for 90 seconds after power returns, not a lockout. It flashes when the furnace is powered up during a heat call, or when the heat call opens during the blower on-delay. The amber LED goes back to continuous on after those 90 seconds if no fault is stored. It is not code 15, the blower-motor lockout, and it is not rapid flashing, which is reversed line polarity.
Likely causes
- 115 V or 24 V power returned while the furnace was in a call for heat
- The call for heat opened during the blower on-delay
How to fix 12: safe DIY steps
- Count 1 short flash and 2 long flashes before you turn the furnace off. This pattern is the 90-second blower run, not a lockout
- Wait out the 90 seconds. The chart says the LED returns to continuous on when no fault is present
- If a different counted code replaces 12, use that code. Do not clear history to erase 12
Capacitors can hold a charge after the power is off. Safety terms.
When to call a pro
Call a licensed HVAC technician if the blower does not stop after the 90 seconds, or if a fault code replaces 12.
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Parts & tools for this fix
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Furnace blower (circulator) motor: guide
In this code: The call for heat opened during the blower on-delay
This one is for a technician to test or replace, so we only explain it and do not link to buy it.