Error Code Code 42

Carrier 58MVP Error Code Code 42: Inducer Outside Valid Speed Range

TL;DR
Indicates the inducer motor is not operating at the calculated RPM, or has not started within 10 seconds after a call for heat. Check wiring to motor; otherwise refer to the troubleshooting guide.
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 42 Mean?

Indicates the inducer motor is not operating at the calculated RPM, or has not started within 10 seconds after a call for heat. Check wiring to motor; otherwise refer to the troubleshooting guide.

Common Causes

Cause Likelihood DIY?
Inducer motor failure or degradation Most common ✗ Call a pro →
Inducer motor wiring issue Common ✗ Call a pro →
Inducer wheel obstruction or frost build-up on combustion-air inlet Common ✗ Call a pro →
Blocked combustion air or vent pipe Common ✓ DIY fix →
Plugged condensate drain Common ✓ DIY fix →
Failed or out-of-calibration pressure switches Uncommon ✗ Call a pro →

When to Call a Professional

Contact a licensed HVAC technician if:

Sources

  1. Carrier 58MVP Service and Maintenance Manual, p.11 – LED Codes
  2. Carrier 58MVP Troubleshooting Guide, p.27–28 – Fault Code 42