Thermistor is reading 0. Not sure about the firmware version. Where do I check that?

Follow up:
After checking it with the printer head heating up, I have voltage to HEAT 0 but I still can't get the thermister to read. HEAT 0 varies wildly between 9 and 14 volts. M2 Quick Start doesnt see the Heat Extruder as heating up but it is hot. Still no voltage to FAN 0.

Long story short, I scored a makergear M2 pre-2015 model with the Z motor mount broken off. I ordered a new motor mount and ran the M2 Quick Start guide. I leveled the bed and the bed heated fine. However it wasnt reading the printer head as heating up. After confirming the head was hot, I figured t...