Error Code Code 45

Carrier 59SC2B Error Code 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 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 Most common ✗ Call a pro →
Flame sense circuit failure Common ✗ Call a pro →
Software check error Common ✗ Call a pro →
Defective control board Uncommon ✗ Call a pro →

When to Call a Professional

Contact a licensed HVAC technician if:

Sources

  1. Carrier 59SC2B Installation & Service Manual (59SC2B-03SI), Fig. 57 - Service Label, p.66; Troubleshooting Guide pp.80-81