My heater/ac air blows out of all vents, has no direction. this is causing less air to come out of defrost. Position knob on dash no long works. need to position fan for defrost

SOURCE: No dashboard heat output

The climate control was poorly designed on these cars.

There is only heat on the floor and defrost settings, due to the layout of the ductwork.

SOURCE: Heater/AC only works thru defroster vents on '98 Contour

you prob have a vac leak on the back of the intake. good luck

SOURCE: 1998 Mustang - AC blows only through Defrost vents

You probably have a vacuum leak on the passenger side. its a small plastic hose some times they come unpluged from the engine. or brake.

SOURCE: '98 Ford Ranger fan function switch not working

I already posted my solution.

SOURCE: PROBLEM WHEN SELECTING THE DIRECTION FOR THE AIR

Sounds like you have a supply vacuum problem. When you lose supply vacuum to the control head it defaults to defrost.