Error Code Status Code 42

Carrier 58MVC Error Code Status Code 42: Inducer Motor Fault

TL;DR
Indicates the inducer has not started within 20 seconds after a call for heat, the inducer RPM is outside its valid range of operation, or the inducer RPM signal was lost for 5 seconds during operation.
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 Status Code 42 Mean?

Indicates the inducer has not started within 20 seconds after a call for heat, the inducer RPM is outside its valid range of operation, or the inducer RPM signal was lost for 5 seconds during operation.

Common Causes

Cause Likelihood DIY?
Inducer motor failure ✗ Call a pro →
Restricted combustion air supply ✓ DIY fix →
Failed inducer motor ✗ Call a pro →
Improper pressure switch wiring ✗ Call a pro →
Inducer wheel rub against inducer housing ✗ Call a pro →
Excessive pressure drop across heat exchangers (blocked) ✗ Call a pro →
Excessive restriction in combustion-air or vent pipe ✓ DIY fix →

When to Call a Professional

Contact a licensed HVAC technician if:

Sources

  1. Carrier 58MVC Series 100 Troubleshooting Guide, p.9 & p.32