Use the illustrations below to help determine if a variable speed motor or board is bad on ICP furnaces "B" revision. An easy way to determine is if the control board has the NFC symbol in the upper right of the control board. 

Helpful tips: With the furnace in idle, back probe and ground the yellow to the motor, it should run full speed. This a GO-NO-GO test. If it does not run, motor is bad.

If blower motor is running at full speed all on its own regardless of thermostat call or adjustments, motor is bad.