Geeetech

Repetier Host does not start the printer but continually says "Heating Extruder". I'm trying to print ABS at 245C. The temperature monitor at the bottom of the panel shows the extruder temperature constantly fluctuating between 12 degrees below the set temperature to 3 degrees above. My room temperature is 36C (Spain). Do I have a problem with the heater or thermostat?

I guess you had better to upgrade the firmware or upload the firmware again due to the randomly starting heating.

Do a PID tune ( http://reprap.org/wiki/PID_Tuning ) and if that doesn't work install a new temp sensor.