Antenna mast replacement failure.

Last summer the toothed plastic leader in my NB antenna mast broke.
When I turned the radio on or off, the motor in the trunk would whir
for 10-15 seconds but the antenna didn't move. So I unplugged the
three-wire connector from the motor assembly and left the antenna in
the "up" position over the winter.

This week I got a replacement mast, and followed the generally
accepted replacement procedure: take motor assembly out of trunk,
disassemble it, remove old toothed plastic leader, re-install motor
assembly in trunk. But, when I got to the point where you try to feed
in the new mast/leader I get nothing. There's just dead silence from
the motor assembly when I turn the radio on and off -- it doesn't even
try to move.

The owner's manual shows two fuses labelled "auto antenna" (one under
the hood, one next to the driver's left knee). Both are OK.

I took the motor assembly apart again and I can spin the motor shaft
by hand and it spins freely and feels like a high-speed DC motor is
supposed to feel.

Since I had it appart anyway, I reassembled it with the antenna mast
installed in the down position (seems a bit simpler than trying to
feed the leader in while the motor is spinning).

But, the motor still doesn't spin.

Any ideas what to do next?

--
Grant