How House Works

Carrier furnace code 45 (4 short, 5 long): control circuitry lockout

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

Furnace control LED

45

“CONTROL CIRCUITRY LOCKOUT”

Printed on 17 model series · 26 documents

58MCB, 58STA/58STX, PG8MAA/PG8JAA, 58SB0A/58SC0A, 810SA, PG80ESAA, 820SA, 58TP0A, 58TN0A, 880TA, 59SC2D, 59SC5A, 59SP5A, 59SC5B, 59SP6A, 59TP6A/59TP6B, PG96VAT, 59TN6B, 986TC, 59MN7B, Guide TG-GFC80-02 (models not listed), 59MN7A Series 100, 58MVP/58MVB/58UVB · 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; TG-GFC80-02 p. 8; 59MN7A-01T p. 9; 58-06T p. 8

Technician

What it means

Code 45 is four short flashes followed by five long ones. The labels call it “CONTROL CIRCUITRY LOCKOUT”; the 59SU5A, Bryant 935SA, 59CU5A and Payne PG80ESU labels spell it “CIRCUITARY” 59SU5A-05SI, p. 51; 59CU5A-01SI, p. 65; GFULN80-G-01TS, p. 7. The control has locked out for one hour because of a gas valve relay stuck open, a flame sense circuit failure or a software check error, and resets itself after that hour 58SC0A-05SI, p. 26. The label’s instruction is: “Reset power to clear lockout. Replace control if status code repeats.” 58SC0A-05SI, p. 26.

Check these first

The causes on the 45 label are in the furnace control, and the owner’s manuals do not mention code 45. They do not give the label’s power reset as an owner step, and the label’s next step, replacing the control, is technician work. From the owner’s manual you have the 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. If the furnace still fails to operate, call your service representative OM9GFRC-02, p. 11. Carrier’s Furnace Repair article asks owners to read the flash code and tell the technician.

When to call a licensed technician

  • The code repeats. The label’s step for that case is to replace the control 58SC0A-05SI, p. 26.
  • The gas valve relay, the flame sense circuit and the control’s software, the three causes on the label 58SC0A-05SI, p. 26.
  • 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 has no code 45 58P_R-9SM, p. 9, and neither does the 58SU0A 58SU0A-05SI, p. 36.
  • On the 59TP6C, 59TP7A, Bryant 926TC, Payne PG96VTAB and 58SP0B displays, 45.1 is “Internal control error”, 45.2 “GVR relay not closing”, 45.3 “Micro EEPROM error” and 45.4 “Micro loss of Comm” 59TP6C-01SI, p. 56; IM-PG96VTAB-01, p. 54; 58SP0B-01SI, p. 30.
  • On the Bryant 800SB and 935SB, 45.1 is “Control failure – flame circuit fault, memory mismatch or sequence error.”, 45.2 is a gas valve relay that will not close, and 45.3 an EEPROM memory issue II800SB-01, p. 31; II935SB-01, p. 48.
  • All five 3-digit tables add: “For code 45, cycle power, if code 45 repeats, replace control.” 59TP6C-01SI, p. 56; IM-PG96VTAB-01, p. 54; 58SP0B-01SI, p. 30; II800SB-01, p. 31; II935SB-01, p. 48.
  • The Infinity zone control lists furnace code 45 as “Control Circuitry Lockout” UIZ01-07SI, p. 20.

Related Carrier codes

  • 45.1 “Internal control error”
  • 45.2 “GVR relay not closing”
  • 21 “GAS HEATING LOCKOUT”

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. 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.
  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. 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.
  25. 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.
  26. 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.
  27. 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.
  28. 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.
  29. 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.
  30. 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.
  31. 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.
  32. 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.
  33. 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.
  34. 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.
  35. 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.
  36. 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.
  37. 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.
  38. 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.
  39. Carrier Corporation. Furnace Repair Service | Signs, Costs & Troubleshooting. Web page; no date printed. Accessed Oct 19, 2026.