You haven't given enough info to diagnose.

If the airway is blocked, the motor load is reduced because
it's not doing anything, hence the motor speeds up, and power
consumption drops.

If the motor is losing power internally (usually due to damage),
the motor slows down, and power consumption increases.

In both cases, the motor can overheat, so that alone doesn't
indicate the cause. The OP gave enough info to identify the
latter (motor is losing power internally -- it could have
started with overheating due to blocked airflow, but if so,
it has gone past that to motor damage now). You haven't
given enough info to identify which scenario applies.

If you momentarily block the airflow of a vacuum cleaner, you
will hear it speed up as in the first case, except that if it
is already blocked, it won't speed up as much as it will
already been running faster than it should. If you are using
a vacuum cleaner you're familiar with, this is a good test to
do occasionally to check for blockage, to make sure you get
the expected speed up if you block the airflow for a couple
of seconds. If the speed up is less than normal, then it is
probably already partially blocked, and that should be
investigated. Don't rely on thermal trips to protect motors;
a big problem with them is that when they trip, cooling
stops instantly, but heat will still be working its way out
from hot areas, and increase temperature of other parts and
damage them during the time the motor is tripped out. (This
is why when you overheat a drill motor, you should run it
for a while at full speed no load to cool it, and not just
stop using it, which is much more likely to wreck it.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]



OP Here........

Thanks for your help all.

I am inclined to think the motor is "borked" because of the high current
usage even on no load

The overheating has been a sudden phenomenon.....though no boubt internal
blockages could have contributed.

Since replacement is apparentluy simple I will pick up a new one in due
course.....and decrud the fan while I am at it.

David