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Carrier gas furnace code 24: 24-volt fuse on the control has blown
Gas furnace, Canada and United States
The 3-amp fuse protecting the furnace's 24-volt control circuit is open. A short in the 24-volt wiring, including the thermostat wires, blows it.
On the status light, this code is 2 short flashes, then 4 long flashes.
This needs a licensed gas technician. There is nothing safe to check yourself. Leave the covers on and book a professional.
What causes it
Standard amber-LED furnaces
-
A short circuit in the 24-volt wiring, including the thermostat wires. A technician disconnects the thermostat wires to find the short and replaces the fuse with a 3-amp fuse only.
Ultra-low NOx furnaces
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A short circuit in the 24-volt wiring. A technician finds the short and replaces the fuse with a 3-amp fuse only.
How to read this code on your unit
The amber status light (red on some older boards) on the furnace control shows through a small window in the blower access door. A steady light means the control has power and no fault to show. A code is two digits. Count the short flashes for the first digit, then the long flashes for the second, so 3 short flashes followed by 3 long flashes is code 33, and 1 short then 1 long is code 11. Write the code down before you open the door or switch the furnace off.
Booking a licensed gas technician
Book a licensed gas technicianlicensed gas technician
- Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
- Note the code, how often it appears, and the model and serial numbers from the rating label.
- Book a licensed gas technician and give them those details.
Models that show this code
328 models in 26 ranges
| Range | Models |
|---|---|
| 58CTA/CTX | 58CTA045-08, 58CTA045-12, 58CTA070-08, 58CTA070-12, 58CTA070-16, 58CTA090-14, 58CTA090-16, 58CTA090-20, 58CTA110-12, 58CTA110-16, 58CTA110-22, 58CTA135-16, 58CTA135-22, 58CTA155-20, 58CTX045-08, 58CTX045-12, 58CTX070-08, 58CTX070-12, 58CTX070-16, 58CTX090-14, 58CTX090-16, 58CTX090-20, 58CTX110-12, 58CTX110-16, 58CTX110-22, 58CTX135-16, 58CTX135-22, 58CTX155-20 |
| 58CVA/CVX | 58CVA070-12, 58CVA090-16, 58CVA110-20, 58CVA135-22, 58CVA155-22, 58CVX070-12, 58CVX090-16, 58CVX110-20, 58CVX135-22, 58CVX155-22 |
| 58DLA/DLX | 58DLA045-08, 58DLA045-12, 58DLA070-08, 58DLA070-12, 58DLA070-16, 58DLA090-14, 58DLA090-16, 58DLA090-20, 58DLA110-12, 58DLA110-16, 58DLA110-22, 58DLA135-16, 58DLA135-22, 58DLA155-20, 58DLX045-08, 58DLX045-12, 58DLX070-08, 58DLX070-12, 58DLX070-16, 58DLX090-14, 58DLX090-16, 58DLX090-20, 58DLX110-12, 58DLX110-16, 58DLX110-22, 58DLX135-16, 58DLX135-22, 58DLX155-20 |
| 58SB0A/58SB1A | 58SB0A045E14-12, 58SB0A045E17-12, 58SB0A070E14-12, 58SB0A070E17-12, 58SB0A070E17-16, 58SB0A070E21-16, 58SB0A090E17-14, 58SB0A090E21-16, 58SB0A090E21-20, 58SB0A090E24-20, 58SB0A110E21-20, 58SB0A110E24-20, 58SB0A135E24-20, 58SB0A155E24-20, 58SB1A045E14-12, 58SB1A045E17-12, 58SB1A070E14-12, 58SB1A070E17-12, 58SB1A070E17-16, 58SB1A070E21-16, 58SB1A090E17-14, 58SB1A090E21-16, 58SB1A090E21-20, 58SB1A090E24-20, 58SB1A110E21-20, 58SB1A110E24-20, 58SB1A135E24-20, 58SB1A155E24-20 |
| 58SC0A/58SC1A | 58SC0A045E14-12, 58SC0A045E17-12, 58SC0A070E14-12, 58SC0A070E17-12, 58SC0A070E17-16, 58SC0A070E21-16, 58SC0A090E17-14, 58SC0A090E21-16, 58SC0A090E21-20, 58SC0A090E24-20, 58SC0A110E21-20, 58SC0A110E24-20, 58SC0A135E24-20, 58SC1A045E14-12, 58SC1A045E17-12, 58SC1A070E14-12, 58SC1A070E17-12, 58SC1A070E17-16, 58SC1A070E21-16, 58SC1A090E17-14, 58SC1A090E21-16, 58SC1A090E21-20, 58SC1A090E24-20, 58SC1A110E21-20, 58SC1A110E24-20, 58SC1A135E24-20 |
| 58SP0A/58SP1A | 58SP0A045V14-12, 58SP0A045V17-16, 58SP0A070V17-16, 58SP0A070V21-20, 58SP0A090V21-20, 58SP0A090V24-20, 58SP0A110V24-22, 58SP1A045V14-12, 58SP1A045V17-16, 58SP1A070V17-16, 58SP1A070V21-20, 58SP1A090V21-20, 58SP1A090V24-20, 58SP1A110V24-22 |
| 58STA/STX | 58STA045-08, 58STA045-12, 58STA070-08, 58STA070-12, 58STA070-16, 58STA090-14, 58STA090-16, 58STA090-20, 58STA110-12, 58STA110-16, 58STA110-22, 58STA135-16, 58STA135-22, 58STA155-20, 58STX045-08, 58STX045-12, 58STX070-08, 58STX070-12, 58STX070-16, 58STX090-14, 58STX090-16, 58STX090-20, 58STX110-12, 58STX110-16, 58STX110-22, 58STX135-16, 58STX135-22, 58STX155-20 |
| 58TN0A/58TN1A | 58TN0A045C17-12, 58TN0A070C14-12, 58TN0A070C17-16, 58TN0A070C21-20, 58TN0A090C17-16, 58TN0A090C21-20, 58TN0A110C21-20, 58TN0A135C24-22, 58TN1A045C17-12, 58TN1A070C14-12, 58TN1A070C17-16, 58TN1A070C21-20, 58TN1A090C17-16, 58TN1A090C21-20, 58TN1A110C21-20, 58TN1A135C24-22 |
| 58TP0A/58TP1A | 58TP0A045V14-12, 58TP0A070V14-12, 58TP0A070V17-16, 58TP0A090V17-16, 58TP0A090V21-20, 58TP0A110V21-22, 58TP0A135V24-22, 58TP1A045V14-12, 58TP1A070V14-12, 58TP1A070V17-16, 58TP1A090V17-16, 58TP1A090V21-20, 58TP1A110V21-22, 58TP1A135V24-22 |
| 59MN7A | 59MN7A060V17-14, 59MN7A080V17-14, 59MN7A060V21-20, 59MN7A080V21-20, 59MN7A100V21-22, 59MN7A120V24-22 |
| 59MN7B | 59MN7B060C17-14, 59MN7B060C21-20, 59MN7B080C17-14, 59MN7B080C21-20, 59MN7B100C21-22, 59MN7B120C24-22 |
| 59SC2A, 59SC2B and 59SC2C | 59SC2A040E14-10, 59SC2A060E14-10, 59SC2A060E17-14, 59SC2A080E17-16, 59SC2A080E21-20, 59SC2A100E21-14, 59SC2A100E21-20, 59SC2A120E24-20, 59SC2B040E14-10, 59SC2B060E14-12, 59SC2B040E17-12, 59SC2B060E17-16, 59SC2B080E17-16, 59SC2B080E21-20, 59SC2B100E21-16, 59SC2B100E21-22, 59SC2B120E24-22, 59SC2C040E14-10, 59SC2C060E14-12, 59SC2C040E17-12, 59SC2C060E17-16, 59SC2C080E17-16, 59SC2C080E21-20, 59SC2C100E21-16, 59SC2C100E21-20, 59SC2C120E24-20 |
| 59SC2D | 59SC2D040E14-10, 59SC2D040E17-12, 59SC2D060E14-12, 59SC2D060E17-14, 59SC2D080E17-16, 59SC2D080E21-20, 59SC2D100E21-20, 59SC2D100E21-22, 59SC2D120E24-20 |
| 59SC5A | 59SC5A026E14-08, 59SC5A040E14-10, 59SC5A060E14-10, 59SC5A040E17-12, 59SC5A060E17-14, 59SC5A080E17-16, 59SC5A080E21-20, 59SC5A100E21-14, 59SC5A100E21-20, 59SC5A120E24-20, 59SC5A140E24-20 |
| 59SC5B | 59SC5B026E14-10, 59SC5B040E14-10, 59SC5B040E17-12, 59SC5B060E14-12, 59SC5B060E17-16, 59SC5B080E17-16, 59SC5B080E21-20, 59SC5B100E21-20, 59SC5B100E21-22, 59SC5B120E24-22, 59SC5B140E24-22 |
| 59SP5A | 59SP5A026E14-10, 59SP5A040E14-10, 59SP5A060E14-12, 59SP5A040E17-12, 59SP5A060E17-14, 59SP5A080E17-16, 59SP5A080E21-20, 59SP5A100E21-20, 59SP5A120E24-22 |
| 59SP6A | 59SP6A040V14-10, 59SP6A040V17-12, 59SP6A060V14-12, 59SP6A060V17-14, 59SP6A080V17-16, 59SP6A080V21-20, 59SP6A100V21-20, 59SP6A120V24-22 |
| 59TN6A | 59TN6A060V17-14, 59TN6A080V17-14, 59TN6A080V21-20, 59TN6A100V21-22, 59TN6A120V24-22 |
| 59TN6B | 59TN6B060C17-14, 59TN6B080C17-14, 59TN6B080C21-20, 59TN6B100C21-22, 59TN6B120C24-22 |
| 59TP5A | 59TP5A040E14-10, 59TP5A060E14-12, 59TP5A040E17-12, 59TP5A060E17-14, 59TP5A080E17-16, 59TP5A080E21-20, 59TP5A100E21-20, 59TP5A120E24-22 |
| 59TP6A | 59TP6A040V14-10, 59TP6A040V14-12, 59TP6A060V17-12, 59TP6A060V17-14, 59TP6A080V17-16, 59TP6A080V21-20, 59TP6A100V21-20, 59TP6A120V24-22 |
| 59TP6B | 59TP6B040V14-10, 59TP6B040V17-12, 59TP6B060V14-12, 59TP6B060V17-14, 59TP6B080V17-16, 59TP6B080V21-20, 59TP6B100V21-20, 59TP6B120V24-22 |
| 58CU0A | 58CU0A040C17-12, 58CU0A060C17-16, 58CU0A080C21-20, 58CU0A100C21-20 |
| 58SU0A | 58SU0A040E17-12, 58SU0A060E17-16, 58SU0A080E21-20, 58SU0A100E21-20 |
| 59CU5A | 59CU5A060C17-16, 59CU5A080C21-20, 59CU5A100C21-22 |
| 59SU5A | 59SU5A040E17-12, 59SU5A060E17-16, 59SU5A080E21-20, 59SU5A100E21-20, 59SU5A100E21-22 |
Where this comes from
- 59SC5A single-stage condensing gas furnace, installation, start-up, operating and service instructions (59SC5A-13SI) , page 67, 73, 83
- 59TP6A two-stage variable-speed condensing gas furnace, installation, start-up, operating and service instructions (59TP6A-10SI) , page 90
- 58SU0A 80% single-stage ultra-low NOx gas furnace, installation, start-up, operating and service instructions (58SU0A-06SI) , page 33
- 59SU5A single-stage ultra-low NOx condensing gas furnace, installation, start-up, operating and service instructions (59SU5A-05SI) , page 51
- 58CU0A 80% communicating ultra-low NOx gas furnace, installation, start-up, operating and service instructions (58CU0A-03SI) , page 31
- 59CU5A single-stage communicating ultra-low NOx condensing gas furnace, installation, start-up, operating and service instructions (59CU5A-01SI) , page 65
Checked against the manufacturer's manual on 9 October 2026.
Other Carrier gas furnace codes
| Code | Meaning | What you can do |
|---|---|---|
| 14 | Ignition lockout after repeated failed lighting attempts | Safe checks first, then a pro |
| 15 | Blower motor lockout | Call a pro |
| 21 | Gas heating lockout, fault in the gas valve circuit | Safe checks first, then a pro |
| 22 | Flame sensed while the gas valve is off | Safe checks first, then a pro |
| 23 | Flue or venting fault (depends on model) | Call a pro |
| 25 | Model plug missing or wrong, or a setup switch error | Call a pro |
| 26 | Burner thermal switch open | Call a pro |
| 31 | Flue or venting fault (depends on model) | Safe checks first, then a pro |
| 32 | Low or low-heat pressure switch did not close, or opened again | Safe checks first, then a pro |
| 10.1 | Line voltage polarity reversed | Call a pro |
| 24.1 | Fuse fault, short in the 24-volt wiring | Call a pro |
| amber light flashing rapidly | Line voltage polarity reversed or the furnace is not grounded | Call a pro |
See all electrical fault codes on gas furnaces across brands.