strange reprap issues, need ideas

Hi all,
I have been working on this issue for quite some time. Im using Repsnapper in conjunction with reprap boards Gen3. I have setup all my axes and they all work when manually moved. The extruder motor runs when told to manually. The issue comes when I manually try to turn on the heater. Repsnapper sends M104 S220. Nothing happens. No lights turn on and nichrome is cold. Now your instant thought is bad mosfet, Right?

Well if I load a model and print the code, my mendel immediately begins printing the model and the heater light comes on sporadicly for very short periods of time then goes back off. If anyone has a clue of whats going on please help as this is my senior project for college and has been 8 months going and needs to be done in may.

What temperature are you reading?

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Sorry meant to mention that, Im reading 0

Then your temperature sensing circuit also has a problem!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Thermistor might not be connected properly. That's the reading (very large resistance=very low T) when you disconnect the thermistor.

If its a techzone, I have this here and there. Prob is the cat-5 connector (at least for me)

check the repsnapper code. mine was by default to get the temp up to 70ºC. dont know why. so I would see the same behavior you're talking about. copy paste the gcode to some text editor and look for all the M104 entries. see if you got something like that.

you can run the hotend separate from the rest of the electronics. i have my hotend connected to a different power supply. you can defently print that way. you gotta do the temp control yourself (in my case i need no tempo control, my hotend top temperature is exactly what i need for printing) but try to check the generated code first.