If it was the monovalve, then wouldn't it keep blowing hot? I thought when the monovalve dies failure mode results in full on heat? Oh yeah, come to think of it, doesn't the schematic show when A/C is in full cold detent then the heater core airflow is cut off? That might make sense then. Isn't the monovalve just a solenoid with a plunger on the bottom of it? Should be easy to trouble shoot and repair.
Yeah I never swap out a $140 part if I can fix a component. I was really proud of myself the other day, I fixed a stereo remote control with a bad switch in only an hour, probably could have bought a new one for $5. Oh well... Too much time on my hands this summer I guess.

Regards,

Theo

klakka klakka klakka klakka...Arf arf arf...
The dog always knows when Theo's home!