The high temperature reading for your ambient temperature display is likely caused by the temperature sensing wire shorted to ground. The temperature sensor is a resistor that varies with temperature. One wire to it is the signal wire to the climate control head and the other wire is a ground connection. With the sensor disconnected, there should be a five-volt reading on the light green with black stripe wire. This is the signal wire. If the voltage is low, disconnect the electrical connector on the back of the climate control head and test the signal wire for continuity to ground. If there is continuity to ground, then the wire has rubbed through to a metal part on the car. There should be no continuity. Trace the wire harness back, looking for places where it may have rubbed through. If there was no continuity to ground, the problem is internal in the climate control head.