I just installed a new hot end (J-Head MK-V) on my Prusa I3, made no other changes, and Pronterface is telling me that the temp on the hotend is 200 when it is cold! I measured the resistance of the thermistor and get 106K which is the same as what the old one got. When I turn on the hotend this resistance falls. And finally, when I connect the old thermistor...same bogus reading being returned. When I connect the hot point thermistor to the bed pins it is read correctly. Could I have somehow fried the circuit for the hot end reading? I dont know Marlin well enough to know how to move the pins for the thermistor to the free set on the Ramps board....

Cheers, Wisar

Edited 1 time(s). Last edit at 02/17/2014 06:53AM by Wisar.

have you tried plugging it into the heated bed thermistor pin to see what it says?

More on this situation. For grins and giggles decided to plug Ramps board into a spare Arduino Mega. Proper temps now being returned all around. Am wondering if a pin got fried on the Arduino?

Wisar