start from monovalve

there are two wires coming out of monovalve. without starting engine, use multimeter to check the resistance of between the wire. if it's infinite, the monovalve is burnt.

if this step is no issue, start engine, turn the hot air button on, measure the wires voltage; if it's not between 12-14vdc, the control is a failure.

climate control involve with electronic board, that's a hard part. there are also some contact-points, if you are lucky, you can clean up those touch-points with "Deoxiit" and get those back to life.

otherwise, go get a climate control assembly from junkyard or ebay, replace the whole unit.

good luck...