I have a 1997 Legacy L 2.2 with 180,000. Since I've had the car (125,000), the vent buttons behave sporadically. Sometimes everything works fine, but often the indicator lights go out, and the buttons don't switch where the air is routed (i.e., can't change from defrost to floor, etc). The hot/cool lever switch still works, and the fan settings work, but when this happens, i'm stuck with the air blowing in its current position. Sucks (and dangerous) when i need some defrost and it's set to floor.
Now, my AC needs a recharge (and it may have it's own set of issues...i can't tell if it is also sporadically cooling, but it's never really "cold" so i think a recharge should do it) so this test may not be good, but it seems that when this problem happens, even though the AC button light no longer works, it seems to be switching on and off, unlike the routing buttons. (i hear some sort of noise behind the glove box activating)
Also, the recirculation button does not seem to work during these times.
It seems to be random when this occurs. Sometimes the lights/functionality go out midway through a drive. Sometimes it's when i start the car. Sometimes I start the car, and it works again.
Per the bulb replacement instructions (http://www.scoobymods.com/forums/legacy_hvac_bulb_replacement-t91.html?t=91), I may just pull the control unit out and see if there's some loose wiring, but it's probably deeper than this. I'm never this lucky.
Also, quick question...the only lights that ever work are the indicator lights under the buttons...I think the entire pictograph on the button is supposed to light up (?). I may replace the bulbs...even though they only work occasionally (hrm).
