Odd Issue with extruder temp

[rostockmax2013]

So when I initiate the extruder heat up (step before extruding a small amount of filament), everything goes fine, the temp curve reads an increase. But then the temp starts reading a decrease in temp!

Has anyone had this issue? If not, what could it be? faulty wiring? bad thermistor?

* i did add 22 gauge wire to extend the thermistor wire, but it shouldn't be an issue, right?


On a side note, where do you change the z axis distance? I could only find the printer config in repetier.
The issue is that the tip of the extruder is 20.1 mm away from touching the build plate at z0.
I did increase the printer size in the basic printer shape/settings page to 365.1 , because at that measurement the extruder would reach the build plate surface spot on at z0. Is this wrong? I did put the command to go to z0, but it goes back to the "old" z0, which is that 20.1 mm from the build plate. Where extactly do i go to change the z "0" measurement? or is it done through the adjustment screws?


Any info would help.