Problem with Min temp and nozzle not heating up

[sit_hein]

I am setting up I3 pro B with ramps 1.4 and sometimes having error message "Min Temp" but sometimes, no error. And Nozzle is not heating up but voltage is showing 11.93V on wire. However, heat bed is working fine. Both control from computer and LCD panel have the same nozzle temperature problem. I need help with this!!!

[zhangxueyou]

When thermistor is not well connected or open circuit, LCD will show "min error", please check the connection of thermistor, and check if extruder thermistor is fine.

[sit_hein]

i ald check thermistor. It is ok. Even if thermistor is not working, extruder should heat up. Isn't it? I had checked with own thermometer and extruder is not physically heating up.

[zhangxueyou]

Both extruder and heat bed can not work with "min error". Please use a mutimeter to check the resistance of thermistor in room temperature.

[sit_hein]

What is the value for resistance of thermistor in room temp?

[zhangxueyou]

About 100K when the temperature is 25°C

[zhangxueyou]

If the value you get is 0 when you test at the 2 endstop of thermistor wires, we can conclude that somewhere of thermistor is open circuit.

[sit_hein]

Now i already got the rootcause. Resistance tested and thermistor is working fine. Problem is coming from extruder heating wire clamp. I am disappointed with how they loosley clamp the two wires near extruder end. Even i tried to reconnect the wires, the clamper is too bad and cannot make it. Might need new hot end.

[zhangxueyou]

What is the resistance of heating wire? It's about 4.5 ohm if it's fine. What is the LCD displaying?

[sit_hein]

I can't even measure resistance and both continuity test as it is loose in clamp near exturuder. Looks physically ok but inside, no connection at all.