Lumia Temperature Gauge

My Lumia Temperature Gauge will read Hot when the Fan is turned on and Heat dial turned to Red for heating. When the heating dial is turned to Blue(cool) and Fan turned or left off....then Temp gauge is ok. Any idea why?

Welcome to AF, sounds like someone may have "monkeyed" with the dash wiring or the inst cluster has a bad ground. BTW, please post the year when opening a thread.