Error Code 24
Carrier 59SC5A Error Code 24: Secondary Voltage Fuse Is Open
TL;DR
Check for short circuit in secondary voltage (24VAC) wiring. Disclaimer
This article is for informational purposes only and does not guarantee the accuracy or completeness of the information provided. Always turn off power and gas supply before attempting any repairs. If you smell gas, leave immediately and call your gas company. Consult a licensed HVAC technician for diagnosis and repair. Any actions taken based on this information are at your own risk. What Does Code 24 Mean?
Check for short circuit in secondary voltage (24VAC) wiring.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Short circuit in thermostat wiring | Most common | ✗ Call a pro → |
| Short in low-voltage accessory wiring | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Basic troubleshooting did not resolve the error
- You smell gas at any point during the process
- You are not comfortable working around gas lines or electrical components
- The unit needs a gas valve, control board, or motor replacement