Carrier Error Code 24: Secondary Voltage Fuse
How to Fix Carrier Code 24
- Step 1: Check your thermostat batteries. Replace them if they are old or weak.
- Step 2: Inspect the wiring connections at the thermostat. Make sure all wires are securely connected.
- Step 3: Reset the system by turning off the power at the breaker for 5 minutes, then turn it back on. If the error returns, call a qualified HVAC technician.
How to Reset Carrier Code 24
- Turn off the furnace power switch, usually located on or near the unit.
- Turn off the circuit breaker for the furnace. Wait 30 seconds.
- Restore power at the breaker and flip the furnace switch back on.
- Set the thermostat to call for heat. If the error code returns after 2-3 ignition attempts, the fault requires repair.
What does 24 mean?
The Carrier error code 24, or a blinking LED pattern of 2 long flashes followed by 4 short flashes, indicates a problem with the secondary voltage fuse. This fuse protects the low-voltage components of your Carrier system, such as the control board, sensors, and sometimes the thermostat. When this fuse blows, it means there's an overcurrent situation in the low-voltage circuit, which could be caused by a short circuit, a faulty component, or a wiring issue. The system will typically shut down to prevent further damage.
Because this code relates to electrical components, it's important to have a qualified HVAC technician diagnose and repair the problem. They will be able to safely troubleshoot the electrical circuits, identify the cause of the blown fuse, and replace any faulty components. Attempting to fix this yourself without proper training and equipment could be dangerous and could potentially damage your system further.
Affected Models
- Performance Series Furnace
- Comfort Series Furnace
- Infinity Series Furnace
- Performance Series
- Base Series Furnace
- Performance Boost Furnace
- Performance Boost 95 Furnace
- WeatherMaker 8000
- WeatherMaker 9300
- Infinity 80
- WeatherMaker Furnace
- 24ABC6 Air Conditioner
- 25HBC5 Heat Pump
- Performance Series Heat Pump
- Performance Series
- Infinity Series
- Performance Series Heat Pump
- Base Series
- Infinity Series
- Comfort Series
- Infinity Series Heat Pump
- Comfort Series Heat Pump
- Infinity 20 Heat Pump with Greenspeed Intelligence
- Comfort 80 Gas Furnace
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| 3 amp fuse | — | — |
| 24V Transformer | — | — |
| Integrated Control Board | — | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| 11 | No Previous Error | Info |
| 12 | Blower On After Power Up | Warning |
| 13 | Limit/Rollout Fault | Critical |
| 14 | Ignition Lockout | Critical |
| 21 | Gas Heating Lockout | Critical |
| 22 | Abnormal Flame | Critical |
| 23 | Pressure Switch Fault | Warning |
| 31 | High Stage Pressure Fault | Warning |
| 32 | Low Flame Sense | Warning |
| 33 | Limit/Rollout Switch Lockout | Critical |