Carrier 58MVP Error Code 42: Inducer Motor Fault

What Does Code 42 Mean?

Status code 42 on the Carrier 58MVP is an inducer motor fault. It sets when the inducer does not start within 20 seconds of a call for heat, runs outside its valid RPM range, or loses its RPM signal for 5 seconds during operation. The inducer creates the draft that safely vents combustion gases and lets the pressure switches close.

On this variable-capacity furnace the inducer modulates to match the heating stage, so the control watches its RPM closely. A failed inducer motor is the most common cause; restricted combustion air, a vent blockage, or improper vent sizing can also drive the RPM out of range. Because the inducer feeds the pressure-switch logic, an inducer problem can appear alongside pressure-switch codes (23, 31, 32, 43).

Diagnosing and replacing the inducer motor, and inspecting venting, is combustion-safety work for a technician — not a DIY repair.

What You'll Notice

• The furnace does not start heating; you may not hear the inducer spin up at the start of a cycle
• The board LED flashes code 42
• The inducer sounds labored, noisy, or runs at the wrong speed
• Possible signs of a blocked or restricted vent or intake outside

Common Causes

How This Is Diagnosed

A technician verifies the inducer's power and control connections, checks that it starts and reaches its rated RPM, and inspects the exhaust, intake, and combustion-air supply for restriction or improper sizing. A failed inducer is replaced; venting issues are corrected. This is professional combustion-safety work.

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• The inducer does not start or sounds labored at the beginning of a cycle
• The board repeatedly flashes code 42
• The exhaust or intake termination looks blocked or restricted
• The furnace produces no heat

✓ Verified against manufacturer service manual — March 2026