Wiper Problem

The wipers on my '85 quit working on high speed. They work perfectly on
low speed but stop where they're at when switched to high.
Does this sound like a wiper motor problem or in the switch?
I don't know which would be the easiest to fix. My wiper switch is also
part of my windshield washer pump switch, the wiper speed control and the
control arm for the cruise control.
Can the wiper control switch be replaced/repaired without having to hassle
with the rest of the controls on that arm?
jj