Carrier 58MVC Error Code 42: Inducer Motor Fault
What Does Code 42 Mean?
Status code 42 on the Carrier 58MVC indicates an inducer motor fault. The inducer (draft motor) either has not started within 20 seconds after a call for heat, its RPM is outside the valid range of operation, or the RPM signal was lost for 5 seconds during operation.
The inducer motor is essential for safely venting combustion gases out of your home. It creates a draft through the heat exchanger and exhaust piping before, during, and after burner operation. Without proper inducer operation, the furnace cannot ignite.
The most common cause is a failed inducer motor that needs replacement. However, a restricted combustion air supply can also cause the motor to run outside its valid RPM range. Check the vent pipes for blockages before calling a technician. Improper motor wiring is an uncommon cause that typically only occurs after service work.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Failed inducer motor | Most common | ✗ Call a pro → |
| Restricted combustion air supply | Common | ✓ DIY fix → |
| Improper motor wiring | Uncommon | ✗ Call a pro → |
How to Fix It: Check for Vent Restrictions
What You'll Need
Steps
- Turn off electrical power at the breaker and shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF. Turn the gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
- Inspect the exhaust vent and intake pipe outside Go outside and locate where the furnace exhaust vent and combustion air intake pipe exit your home. Check for any blockages such as snow, ice, leaves, bird nests, insect nests, or other debris. Clear any obstructions you find. Make sure the vent terminations have adequate clearance.
- Check for adequate combustion air If your furnace draws combustion air from the surrounding area (not through a direct vent pipe), ensure the furnace room is not sealed off. Open any blocked vents or louvers that supply outside air to the furnace area.
- Listen to the inducer motor Restore power briefly and listen when the thermostat calls for heat. The inducer motor should start within a few seconds. If it does not start at all, makes grinding or squealing noises, or sounds labored, the motor likely needs replacement by a technician.
- Restore power and gas, then test If you cleared vent blockages, turn the gas supply valve to ON and flip the circuit breaker to ON. Set your thermostat to call for heat and listen for the inducer to start and run smoothly.
When to Call a Professional
Contact a licensed HVAC technician if:
- The inducer motor does not start at all
- The motor makes grinding, squealing, or rattling noises
- Vent pipes are clear but code 42 persists
- The motor starts but shuts off or fluctuates during operation
- There has been recent service work that may have affected motor wiring
✓ Verified against manufacturer service manual — March 2026