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Carrier furnace status code · Sources read 2026-10-31

Carrier Furnace Code 12: Blower On After Power Up

By the HVAC Responder Editorial Team

Quoted from Carrier troubleshooting guides, read 2026-10-31. Not reviewed by a licensed HVAC professional.

Code 12 is not a fault. In Carrier's troubleshooting guides it means the blower ran for 90 seconds because the furnace was powered up during a call for heat, or the heat call ended during the blower on-delay. The 59MN7A guide labels it normal operation.

How code 12 looks on the furnace light

On these Carrier furnaces the status light shows code 12 as 1 short flash, then 2 long flashes . The guides explain the pattern:

EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND THE SECOND DIGIT BY THE NUMBER OF LONG FLASHES.

Codes differ between furnace generations, so match the series on your furnace’s rating plate to the guide below.

What Carrier’s guides say code 12 means, by furnace series

58CVA / 58CVX

Carrier form TG-GFC80-02, mid-efficiency variable-speed two-stage furnaces

12 BLOWER ON AFTER POWER UP – (115 VAC or 24 VAC) - Blower runs for 90 seconds, if unit is powered up during a call for heat (R-W/W1 closed) or (R-W/W1 opens) during the blower on-delay period.

58MVP (Series 170 & 180), 58MVB, 58UVB

Carrier form 58-06T, variable-speed two-stage condensing furnaces

12 BLOWER ON AFTER POWER UP – (115 VAC or 24 VAC) - Blower runs for 90 seconds, if unit is powered up during a call for heat (R- W/W1 closed) or (R-W/W1 opens) during the blower on-delay period.

59MN7A (Series 100)

Carrier form 59MN7A-01T, variable-speed modulating condensing furnaces

12 BLOWER ON AFTER POWER UP – (115 VAC or 24 VAC) - Normal operation. Blower runs for 90 seconds, if unit is powered up during a call for heat (R-W/W1 closed) or (R-W/W1 opens) during the blower on-delay period.

Does code 12 reset on its own?

The guides do not describe an automatic reset for this code.

What to do before you call

  • Write the code down before you touch anything. Carrier’s guides start with: “DO NOT REMOVE BLOWER ACCESS PANEL! Record status of AMBER LED.” Turning off power can also clear the code history.
  • Everything else on these lists (gas valve, pressure switches, wiring, venting, the control board) is technician work.

Get the furnace looked at

One call routes you to an independent local heating contractor. Tell them the code and the furnace series, and ask the diagnostic fee up front.

Call (877) 565-3062

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Related codes

All Carrier furnace codes

Furnace guides for the wider symptom

Sources

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