I have a 2010 Mercedes E350 4 magic that when I drive the temperature usually runs at 90 degrees. Lately the temperature will spike to close to 120. If I shut down the hvac system, the temperature shortly returns to normal. There are no cel codes.
The thermostat was replaced last year.. Since the conditions corrects itself when the temperature control panel is turned off, I am thinking it might be the temperature control switch that is near the thermostat.