[xj-s] The MK III saga continues

I tested the vacuum servos for the defrost and center vane. Both will
hold vacuum and move their relative doors.
The defrost solenoid never seems to do anything, but the center door
solenoid makes one on/off cycle when the system is turned on but does
not stay on. As near as I can figure, the defrost motor should be
activated in all modes except defrost. Has anyone on the list had
problems like this with their MK III and is the solution a new control
computer? How about a three position wafer switch for
floor/center/defrost mounted in the glove box?
Tom Wilson 87 convection coupe