Unless I'm overlooking something here (no litature at home so I might be wrong) the switchover valve are under the r/h vent kinda buried under the aspirator motor. I'm believe the later 201 still has a heater comtrol valve in the cowl which is vacum controlled and they leak.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.