At the right hand side of the blower housing there is a small electric
motor that controls the fresh / recirc flap. The positive supply to this
motor is fused with the same fuse as the blower relay coil. So, if the
blower works, the problem is not a blown fuse. The control motor does
not have a relay. I am assuming you do not hear the motor run when you
press "fresh" or "recirc"

At the right hand side of the blower housing you should see three
connectors, a 6 pin for the blower resistors, a 2 pin for the blower and
a 3 pin for the recirculation control motor. Unplug it and measure the
voltage (measure on the cable side, not the blower housing connector)
between the YEL/BLK and body ground with the ignition on. You should see
battery voltage. If you don't, there is an open in the wire somewhere.

Measure continuity between the GRN/RED wire and body ground. With the
switch in RECIRC there should be continuity, with the switch in FRESH
there should not. Measure continuity between the GRN/WHT wire and body
ground. With the switch in FRESH there should be continuity, with the
switch in RECIRC there should not. If either of these tests fail, either
the switch is bad, or there is an open in one of the wires. (You could
have a short to ground as well, but in that case you would hear the
motor running continuously with the switch in either FRESH or RECIRC
mode).

If the above tests did not reveal any problems, there is most likely an
internal fault in the recirculation control motor. In the manual, it is
schematically drawn as having a set of brushes and slip rings, in
reality I suspect it has a set of (two) cams and switches. One switch
opens as the flap reaches the RECIRC position, the other switch opens as
the flap reaches the "FRESH" position. If I were to venture a guess, I
would say the latter switch is broken (always open)