i am having the same problem with my thermistor. i just got my printer yesterday, and it worked fine then. the bed heated up no problem. but i turned it on today and my lcd said the bed was at 95 degrees. the bed was at room temp. i unplug the thermistor and then on the lcd all it says is 83 degrees. thats all i can get out of itby blueblasterleb - Prusa i3 and variants