b5 Blower motor locked rotor

What the control is telling you

The blower motor failed to start 10 times in a row. Furnace will not run. ComfortNet thermostat shows MTR LCKD ROTOR b5.

Applies to: GMVC95/AMVC95 upflow and *CVC9 counterflow two-stage furnaces

Likely causes

• Something jamming the blower wheel
• Seized motor bearings
• Failed blower motor

Test and repair steps

1. Safety turn power off before working on the control or wiring.
2. Spin the blower wheel by hand and look for anything in the housing.
3. Repair or replace the wheel or motor if it is stuck or rubbing.
4. If it spins freely, check the motor shaft turns and replace the motor if needed.

Settings for these units

• Normal status displays (7-segment) · Goodman/Amana GM9S96/AM9S96
• Normal status displays (7-segment) · Goodman/Amana GM9S80/AM9S80
• Normal status displays (7-segment) · Goodman/Amana GM9C96/AM9C96
• Minimum recommended filter size · Goodman/Amana GM9C96/AM9C96

Models that show this code

10 models in Goodman/Amana *MVC95/*CVC9 two-stage ComfortNet

Other codes on the same units

• b1 Lost communication with blower motor
• b2 Blower motor size does not match model data
• b3 Blower motor limiting (power, temperature or speed)
• b4 Blower motor trip (lost rotor control or high current)
• b6 Blower motor over/under voltage or over temperature
• b7 Blower motor missing parameters
• b9 Low indoor airflow
• C1 Low-stage cooling