check all of your vacume lines. this system operates off a single vac. feed
to a canister and then to your controls. if this is unplugged or pinched it
will default to the defrost vents. look around the engine compartment for a
loose or broken vac line. good hunting!

There is a computerized vacuum switch behind the glove box area on some
of these that goes bad. The temporary fix is to route vacuum directly to
the vacuum powered air door that routes air to the front vents in the
dash. I think it is the black hose. The supply line is the purple hose.