If I'm understanding you correctly... if you did apply 12VDC directly to the blower motor and it does not run then your blower motor is bad.
If you didn't apply 12VDC directly to the blower motor then I would look at the high limit switch - if it's bad nothing will start, including the fan. The high limit switch is easily accessible. Disconnect all 12VDC power to the furnace, remove the wires from both sides of the high limit switch and test through it with a meter. You should have continuity through the switch if it's working properly.
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