This is going to sound bad but..... be more specific. Is it blowing heat out the sides and cold from the middle or what? Providing you dont have a electrical failure and have power to the mono valve the only other thing would be either the temp control unit or push button panel. Maybe a bad mono valve itself.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.