Changing extruder Geeetech Prusa I3 Pro B

I need to change the extruder hotend of my Prusa I3 Pro B with a GT2560 card and Marlin firmware. I couldn't found an alternative in Geeetech page, so I tried to buy one in Amazon for the Mk8 extruder:

[www.amazon.es]

The thermistor connector is not the same, but I have checked with a tester that it can be connected to the board. When I turn on the printer, it says that the extruder it's at room temperature, but when I heat up to 180º it heats extruder to a much bigger temperature, it seems as is the thermistor don't measure temperature correctly. How can adjust it? Thanks

Edited 1 time(s). Last edit at 11/17/2016 02:06PM by lolo_aguirre.

If it is a different thermistor (the thing that measures the temperature) you will probably have to change the type in the firmware.

What type of thermistor is it? That's the key, once you locate the thermistor type you can adjust Marlin to reflect that type in the configuration.h file.