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nozzle temp reading 398.3C

Posted: Thu Jan 19, 2017 3:23 am
by Maleny
I have just replaced the hot end on my Mini (Mk1) and now the nozzle will not heat, probably because according to the maintenance screen the nozzle temp is 398.3C, I have checked the wiring conductivity as far as the ribbon cable plug and there is no problem there.
I still have my old unit so replaced it and the same thing is happening.
Next I compared them, they both give the same readings which are heater element resistance 9 ohms and sensor resistance about 114 ohms at room temp.
I have connected a resistor decade box across the sensor wires and slowly reduced the resistance, there is no change in the reading.
I have heated them both with my hot air gun and the resistance rises with the temp so assume they are working OK.
There are no voltage readings between any of the 4 wires at the head but I do see 0.86 volts between the heater wires and the chassis of the printer.
Anyone have any Ideas as to were I go from here?