Error Code 45
Carrier 59SC5A Error Code 45: Control Circuitry Lockout
TL;DR
Auto-reset after one hour lockout due to gas valve relay stuck open, flame sense circuit failure, or software check error. Reset power to clear lockout. Replace control if status code repeats. 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 45 Mean?
Auto-reset after one hour lockout due to gas valve relay stuck open, flame sense circuit failure, or software check error. Reset power to clear lockout. Replace control if status code repeats.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Gas valve relay stuck open | Common | ✗ Call a pro → |
| Flame sense circuit failure | Common | ✗ Call a pro → |
| Software check error | Uncommon | ✗ 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