I don't know these cars, but here are some general principles that
might help...

Does the blower show similar symptoms on heater, or only on A/C
(probably defrost too, since that usually invokes the A/C on cars that
have A/C)?

Does the electromagnetic clutch on the A/C compressor engage?  This is
pretty obvious with the hood open, and in many cars can be discerned
from inside the cabin if you listen close (a click, and a change in
engine note due to the reduced load if the engine is running).

Does the repair manual (probably not the owner's manual) state that the
circuits for the blower and the A/C compressor (which could be on the
same circuit or not) are on a fuse, or a manually resetting circuit
breaker, or a self-resetting circuit breaker?  

Cheers,
--Joe

It sounds like the resistor pack for your blower motor has developed an open
or two.  It's what gives you the different speed settings.
If you can locate the motor itself, the resistor pack is usually a
rectangular piece about 3 or 4 inches wide that is held into the ducting
around the motor by 2 screws, and has an electrical connector on it.

That's how it's set up on my 1999 Altima; I expect it would be similar in
your case.

If you find it, and you have a simple multimeter, you can test the different
traces on the board by figuring out what pins they are connected to on the
connector.  If you don't get continuity on any of them, then that's likely
your problem.

The part is inexpensive, about $40 CDN direct from the dealer.

Hope that helps!