How House Works

Carrier furnace code 12 (1 short, 2 long): blower on after power up

By How House Works EditorialBased on Carrier, Bryant and Payne service labels and manualsChecked against sources Updated

Furnace control LED

12

“BLOWER ON AFTER POWER UP (115 VAC or 24 VAC)”

Printed on 16 model series · 25 documents

58MCB, 58STA/58STX, PG8MAA/PG8JAA, 58SB0A/58SC0A, 810SA, PG80ESAA, 820SA, 58TP0A, 58TN0A, 880TA, 59SC2D, 59SC5A, 59SP5A, 59SC5B, 59SP6A, 59TP6A/59TP6B, PG96VAT, 59MN7B, 59SU5A, 935SA, 59CU5A, PG80ESU · 58MCB-4SM p. 15; 58ST-24SI p. 43; IM-PG8J-17 p. 43; 58SC0A-05SI p. 26; 58SB0A-04SI p. 26; II810SA-05 p. 26; IM-PG80ESA-05 p. 26; IM-PG80ESAA-04 p. 27; II820SA-02 p. 26; 58TP0A-02SI p. 37; 58TN0A-02SI p. 35; II880TA-02 p. 35; 59SC2D-02SI p. 61; 59SC5A-13SI p. 67; 59SP5A-18SI p. 70; 59SC5B-04SI p. 63; 59SP6A-01SI p. 59; 59TP6A-10SI p. 73; 59TP6B_04SI p. 67; IM-PG96VAT-13 p. 70; 59MN7B-02SI p. 73; 59SU5A-05SI p. 51; II935SA-05 p. 51; 59CU5A-01SI p. 65; GFULN80-G-01TS p. 6

Owner can check

Some labels print “(115VAC or 24VAC)” or “(115V AC or 24V AC)”; the words are the same.

What it means

Code 12 is one short flash followed by two long ones. The labels call it “BLOWER ON AFTER POWER UP”: the blower runs for 90 seconds if the furnace is powered up (115 VAC or 24 VAC) while the thermostat is calling for heat, which the label writes as R-W closed, or if that call for heat ends during the blower on-delay 58SC0A-05SI, p. 26. The label describes these two cases and the 90 seconds of blower operation, and lists no causes to check. Carrier’s 59MN7A troubleshooting guide calls it normal operation 59MN7A-01T, p. 8.

Check these first

Carrier’s owner’s manuals do not mention code 12, and its label gives nothing to check, so these are the manual’s general steps:

  1. Write the code down before you turn off the power or remove the blower access door OM9GFRC-02, p. 10. Carrier’s 80% owner’s manual does not mention the LED. How to count the flashes: reading a Carrier code.
  2. If the furnace does not heat, go through the owner’s checklist: the thermostat set above room temperature and to HEAT mode, the fuses and circuit breakers, and the electrical power supply switch OM9GFRC-02, p. 11. Carrier’s 80% manual also asks whether the blower access door is firmly in place 80GSFRN-C-03OM, p. 7.
  3. If the furnace still fails to operate, call your service representative OM9GFRC-02, p. 11.

When to call a licensed technician

  • The furnace still fails to operate after the checklist OM9GFRC-02, p. 11. The labels give no technician checks for code 12 itself.
  • On the 59SU5A, Bryant 935SA and 59CU5A, the 12 label adds that if the burner thermal switch (BTS) is also open, the inducer runs as well 59SU5A-05SI, p. 51; 59CU5A-01SI, p. 65. An open BTS has its own code there, 26, which the label describes as a permanent lockout if the switch is open during a call for heat; its checks (a blocked burner inlet or burner mesh, poor inducer flow, excess wind) are technician items 59SU5A-05SI, p. 51.
  • The owner’s manual lets untrained people clean and replace air filters and says all other operations must be performed by trained service personnel OM9GFRC-02, p. 2.

Notes for different models

  • The 58PAV and 58RAV Series 131 label reads “BLOWER ON AFTER POWER UP (115V OR 24V)” and gives only the first case, power-up during a call for heat 58P_R-9SM, p. 9.
  • Two-stage and modulating labels write the call for heat as R-W/W1 58TN0A-02SI, p. 35; 59TP6A-10SI, p. 73.
  • Boards with a 3-digit display show 12.1, “W on at power up” 59TP6C-01SI, p. 56; IM-PG96VTAB-01, p. 54; 58SP0B-01SI, p. 30; II800SB-01, p. 31. On the Bryant 935SB it reads “W on or BTS open at power up or within 5 minutes” II935SB-01, p. 48. All five 3-digit tables also have 46.1, “Momentary loss of power” 59TP6C-01SI, p. 56; IM-PG96VTAB-01, p. 54; 58SP0B-01SI, p. 30; II800SB-01, p. 31; II935SB-01, p. 48.
  • The 58SU0A has no code 12. Its green flashes report thermostat calls; 1 green flash is “Call for Heating” 58SU0A-05SI, p. 36.

Related Carrier codes

  • 12.1 “W on at power up”
  • 11 “NO PREVIOUS CODE”
  • 46.1 “Momentary loss of power”

See also

Other gas furnaces: Goodman, Lennox, Rheem and Ruud

All Carrier codes

Carrier is a trademark of its owner. How House Works is not affiliated with or endorsed by Carrier.

Sources

  1. Carrier Corporation. Owner's Manual, Condensing Gas Furnace. OM9GFRC-02, edition 04/20; replaces OM9GFRC-01. Accessed Oct 17, 2026.
  2. Carrier Corporation. Owner's Manual, Non-Condensing, 80% AFUE Gas Furnace. 80GSFRN-C-03OM, edition 08/22; replaces OM8GFRC-02. Accessed Oct 17, 2026.
  3. Carrier Corporation. 58PAV, 58RAV Induced-Combustion Furnaces, Service and Maintenance Instructions, Sizes 045-155, Series 131. Form 58P,R-9SM (Catalog No. 535-835), edition 9-94; replaces 58P,R-8SM. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  4. Carrier Corporation. 58MCB 4-Way Multipoise Fixed-Capacity Condensing Gas Furnace, Service and Maintenance Instructions, Sizes 040-120, Series 110 & 120. 58MCB-4SM, edition 10/09; replaces 58MCB-3SM. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  5. Carrier Corporation. 58STA/STX Single-Stage Deluxe, Induced-Combustion 4-Way Multipoise Gas Furnace, Series 160. 58ST-24SI, edition 08/13; replaces 58ST-23SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  6. Payne Heating & Cooling. PG8MAA/PG8JAA Series G: Single-Stage Deluxe, Induced-Combustion 4-Way Multipoise Gas Furnace. IM-PG8J-17, edition 08/13; replaces IM-PG8J-16. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  7. Carrier Corporation. 58SC0A/58SC1A: 80% AFUE, Single-Stage, Multi-Speed ECM, 4-Way Multipoise, Non-Condensing Gas Furnace. 58SC0A-05SI REV B, edition 09/21; replaces 58SC0A-05SI REV A. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  8. Carrier Corporation. 58SB0A/58SB1A: Single Stage, Multi-Speed ECM, Non-Condensing Gas Furnace, Input Capacities 45,000 thru 155,000 Btuh. 58SB0A-04SI, edition 03/20; replaces 58SB0A-03SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  9. Bryant Heating & Cooling Systems. 810SA/811SA: 80% AFUE, Single-Stage, Multi-Speed ECM, 4-Way Multipoise, Non-Condensing Gas Furnace. II810SA-05 REV B, edition 09/21; replaces II810SA-05 REV A. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  10. Payne Heating & Cooling. PG80ESAA/PG80ESLA: 80% AFUE, Single-Stage, Multi-Speed ECM, 4-Way Multipoise, Non-Condensing Gas Furnace. IM-PG80ESA-05 REV B, edition 08/21; replaces IM-PG80ESAA-05 REV A. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  11. Payne Heating & Cooling. PG80ESAA/PG80ESLA: Single Stage, Multi-Speed ECM, Non-Condensing Gas Furnace, Input Capacities 45,000 thru 155,000 Btuh. IM-PG80ESAA-04, edition 03/20; replaces IM-PG80ESAA-03. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  12. Bryant Heating & Cooling Systems. 820SA/821SA: 80% AFUE, Non-Communicating, Single Stage, ECM Motor, Variable Speed, 4-Way Multipoise, Non-Condensing Gas Furnace. II820SA-02 REV A, edition 08/21; replaces II820SA-02. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  13. Carrier Corporation. 58TP0A/58TP1A Variable-Speed, ECM Induced-Combustion, 2-Stage 4-Way Multipoise, Non-Condensing Gas Furnace, Series A. 58TP0A-02SI, edition 07/19; replaces 58TP0A-01SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  14. Carrier Corporation. 58TN0A/58TN1A: 80% AFUE, Two-Stage, Variable-Speed 4-Way Multipoise, Non-Condensing Gas Furnace, Series A. 58TN0A-02SI REV A, edition 08/21; replaces 58TN0A-02SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  15. Bryant Heating & Cooling Systems. 880TA/881TA: 80% AFUE, Two-Stage, Variable-Speed 4-Way Multipoise, Non-Condensing Gas Furnace, Series A. II880TA-02 REV A, edition 08/21; replaces II880TA-02. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  16. Carrier Corporation. 59SC2D Single Stage, 35-in. (889 mm) Tall 4-Way Multipoise Condensing Gas Furnace. 59SC2D-02SI, edition 11/19; replaces 59SC2D-01BSI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  17. Carrier Corporation. 59SC5A Single Stage 4-Way Multipoise Condensing Gas Furnace, Series 1 and 2. 59SC5A-13SI, edition 01/19; replaces 59SC5A-12SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  18. Carrier Corporation. 59SP5A Single Stage, 4-Way Multipoise Condensing Gas Furnace, Series 1 and 2. 59SP5A-18SI, edition 01/19; replaces 59SP5A-17SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  19. Carrier Corporation. 59SC5B: Single-Stage, High Efficiency, 4-Way Multipoise, 35-in. (889 mm), Condensing Gas Furnace. 59SC5B-04SI REV E, edition 06/23; replaces 59SC5B-04SI REV D. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  20. Carrier Corporation. 59SP6A: Single-Stage, Non-Communicating, Variable-Speed, ECM Multipoise, Condensing Gas Furnace. 59SP6A-01SI REV D, edition 06/23; replaces 59SP6A-01SI REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  21. Carrier Corporation. 59TP6A Two-Stage Variable Speed ECM Multipoise Condensing Gas Furnace, Series 2, All Series 3 80-20, 100-20, 120-22. 59TP6A-10SI, edition 11/18; replaces 59TP6A-09SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  22. Carrier Corporation. 59TP6B: Installation, Start-up, Operating and Service and Maintenance Instructions. 59TP6B-04SI REV D, edition 06/23; replaces 59TP6B-04SI REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 19, 2026.
  23. Payne Heating & Cooling. PG96VAT: Two-Stage 4-Way Multipoise Condensing Gas Furnace, Series B, All Series C, Sizes 60080, 60100, 66120. IM-PG96VAT-13, edition 11/18. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  24. Carrier Corporation. 59MN7B: Modulating, High Efficiency Condensing Gas Furnace, 4-Way Multipoise. 59MN7B-02SI REV D, edition 06/23; replaces 59MN7B-02SI REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  25. Carrier Corporation. 59SU5A: Up to 95% AFUE, Single-Stage, Upflow/Horizontal, Ultra Low NOx, 35-in. Tall, Condensing Gas Furnace (Minor Series 2). 59SU5A-05SI REV D, edition 06/23; replaces 59SU5A-05SI REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  26. Bryant Heating & Cooling Systems. 935SA: Up to 95% AFUE, Single-Stage, Upflow/Horizontal, Ultra Low NOx, 35-in. Tall, Condensing Gas Furnace (Minor Series B). II935SA-05 REV D, edition 06/23; replaces II935SA-05 REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  27. Carrier Corporation. 59CU5A: Single-Stage, Upflow/Horizontal Communicating, Variable Speed ECM, Ultra Low NOx, 35-in Tall Condensing Gas Furnace. 59CU5A-01SI REV D, edition 06/23; replaces 59CU5A-01SI REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  28. Carrier Corporation. 58SU0A 4-Way Multipoise, Ultra Low NOx 80% AFUE Gas Furnace, Input Capacities 40,000 thru 100,000 Btuh. 58SU0A-05SI, edition 11/19; replaces 58SU0A-04SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  29. Payne Heating & Cooling. PG80ESU (Minor Series B&C) Troubleshooting Guide: 80% AFUE, Ultra Low NOx, 4-Way Multipoise Gas Furnace. GFULN80-G-01TS, edition 08/23. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  30. Carrier Corporation. 59MN7A Series 100 Troubleshooting Guide: Variable Speed, Modulating Electronic Condensing Four-Way Multipoise Gas Furnace. Form 59MN7A-01T, edition 9-11. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 19, 2026.
  31. Carrier Corporation. 59TP6C: Two-Stage, Non-Communicating, Variable 25-Speed, ECM Multipoise, Condensing Gas Furnace with InteliSense. 59TP6C-01SI REV A, edition 06/23; replaces 59TP6C-01SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  32. Payne Heating & Cooling. PG96VTAB: Two-Stage, Non-Communicating, Variable 25-Speed, ECM Multipoise, Condensing Gas Furnace. IM-PG96VTAB-01 REV A, edition 06/23; replaces IM-PG96VTAB-01. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  33. Carrier Corporation. 58SP0B/58SP1B: 80% AFUE, Non-Communicating, Single Stage, Variable 25-Speed, ECM Motor, 4-Way Multipoise, Non-Condensing Gas Furnace with InteliSense. 58SP0B-01SI, edition 03/23. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  34. Bryant Heating & Cooling Systems. 800SB/801SB: 80% AFUE, Single Stage, Multi-Speed ECM, 4-Way Multipoise, Non-Condensing Gas Furnace. II800SB-01 REV B, edition 06/23; replaces II800SB-01 REV A. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  35. Bryant Heating & Cooling Systems. 935SB: Installation, Start-up, Operating and Service Maintenance Instructions (single-stage ultra low NOx condensing; 3-digit display). II935SB-01 REV C, edition 06/23; replaces II935SB-01 REV B. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 19, 2026.