How House Works

Carrier furnace code 24 (2 short, 4 long): secondary voltage fuse

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

Furnace control LED

24

“SECONDARY VOLTAGE FUSE IS OPEN”

Printed on 21 model series · 31 documents

58PAV/58RAV Series 131, 58MCB, 58STA/58STX, PG8MAA/PG8JAA, 58SB0A/58SC0A, 810SA, PG80ESAA, 820SA, 58TP0A, 58TN0A, 880TA, 59SC2D, 59SC5A, 59SP5A, 59SC5B, 59SP6A, 59TP6A/59TP6B, PG96VAT, 59TN6B, 986TC, 59MN7B, 59SU5A, 935SA, 59CU5A, PG80ESU, Guide TG-GFC80-02 (models not listed), 59MN7A Series 100, 58MVP/58MVB/58UVB · 58P_R-9SM p. 9; 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; 59TN6B-01SI p. 60; II986TC-01 p. 60; 59MN7B-02SI p. 73; 59SU5A-05SI p. 51; II935SA-05 p. 51; 59CU5A-01SI p. 65; GFULN80-G-01TS p. 6; TG-GFC80-02 p. 7; 59MN7A-01T p. 8; 58-06T p. 7

Technician

What it means

Code 24 is two short flashes followed by four long ones. Every two-digit label calls it “SECONDARY VOLTAGE FUSE IS OPEN” and gives one check: a short circuit in the secondary voltage (24 VAC) wiring 58SC0A-05SI, p. 26. Carrier’s 59MN7A guide includes the thermostat leads in that wiring 59MN7A-01T, p. 8.

Check these first

The owner’s manuals do not mention code 24, and the label’s only check is wiring work for a technician. What the owner’s manual gives you is its general checklist:

  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. Check that the thermostat is set above room temperature and to HEAT mode OM9GFRC-02, p. 11.
  3. Check the fuses and circuit breakers, and that the electrical power supply switch is on OM9GFRC-02, p. 11.
  4. Call your servicing dealer and give the model and serial numbers of the furnace 80GSFRN-C-03OM, p. 7; OM9GFRC-02, p. 11.

When to call a licensed technician

  • Finding the short circuit in the 24 VAC wiring, which on the 59MN7A includes the thermostat leads 58SC0A-05SI, p. 26; 59MN7A-01T, p. 8.
  • Anything on the furnace control, including its fuse. Carrier’s condensing 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

  • Carrier’s 80% owner’s manual lists “Are any fuses blown? (There is a fuse on the furnace control.)” in its checklist 80GSFRN-C-03OM, p. 7. It gives no steps for reaching or replacing that fuse, so this page treats the control fuse as technician work.
  • Boards with a 3-digit display show 24.1, “Fuse fault” 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 24. Its 3 amber flashes are “Control Fuse Open”, and the label adds that operation continues after the fault is corrected 58SU0A-05SI, p. 36.
  • The Infinity zone control lists furnace code 24 as “Secondary Voltage Fuse Open” UIZ01-07SI, p. 20.

Related Carrier codes

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. SYSTXCCUIZ01--V Infinity Control (Zone), Installation Instructions. UIZ01-07SI, edition 05/12; replaces UIZ01-06SI. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  18. 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.
  19. 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.
  20. 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.
  21. 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.
  22. 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.
  23. 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.
  24. 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.
  25. Carrier Corporation. 59TN6B: Two-Stage, Variable-Speed, Multipoise, 35 in. (889 mm) Tall, Condensing Gas Furnace. 59TN6B-01SI REV D, edition 06/23; replaces 59TN6B-01SI REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  26. Bryant Heating & Cooling Systems. 986TC: Two-Stage, Variable-Speed, Multipoise, 35 in. (889 mm) Tall, Condensing Gas Furnace. II986TC-01 REV D, edition 06/23; replaces II986TC-01 REV C. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  27. 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.
  28. 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.
  29. 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.
  30. 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.
  31. 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.
  32. 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.
  33. Carrier Corporation. Troubleshooting Guide: Mid-Efficiency Variable-Speed, Two-Stage Induced-Combustion Deluxe, 4-Way Multipoise Gas Furnace. TG-GFC80-02, edition 05/18; replaces TG-GFC80-01. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 17, 2026.
  34. 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.
  35. Carrier Corporation. 58MVP Series 170 & 180, 58MVB, 58UVB Troubleshooting Guide: Variable Speed, Two-Stage Electronic Condensing Gas Furnace. Form 58-06T, edition 6-08; replaces 58MVP-10SM. Manufacturer PDF hosted on shareddocs.com, not on the brand website.. Accessed Oct 19, 2026.
  36. 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.
  37. 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.
  38. 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.
  39. 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.
  40. 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.