Replaced hot end and now get vssa fault

[chriskimbr]

@veti The hot end with thermistor came with no documentation.

[Veti]

then you prob need to either

• measure the resistance at 50 and 240 degrees using a calibrated temperature sensor.
• buy a thermistor with documentation
• live with inaccuracies that could range around 40 degrees

[chriskimbr]

@veti Im going to get a cheap hot end and thermistor from local store to test and see if im having same problem.
from what your telling me , i need to look at thermisor table and set the 'C' value ?

[Veti]

you can use the configurator tool to calculate the values

https://configurator.reprapfirmware.org/Heaters

[chriskimbr]

@veti so the setting for thermistor isnt causing the vssa fault?

[Veti]

wrong B and C values will just give you wrong temperature reading. 2000 means there is no reading

[dc42]

The Vssa fault message means that the Vssa line, which should be very close to ground potential, is actually closer to +3.3V.

The usual cause of this is a short between the side of the thermistor that is connected to Vssa, and the hot end heater or bed heater. So if you get a Vssa fault report, disconnect the thermistors one at a time. Then you will be able to tell which thermistor has the short to a heater.

If you disconnect all the thermistors and you still get the Vssa fault, then either the Vssa polyfuse is open circuit, or the Vssa sense series resistor is open circuit.

[chriskimbr]

@dc42 if i dissconnect the hot end thermo the bed thermo works fine

[chriskimbr]

Good lessons learned here.
Thanks for all your input and help.

I went to local shop and bought another hot end assembly.
Narrowed it down to the Thermistor wire is bad. The new thermistor works with no fault!!!

Is it common to get bad Thermistor wires? Is there something i may have to to damage it?

See temps!!! No faults!

The culprit! Day waisted thanks to this guy and gearbest🤬

[Veti]

you need to be aware of the quality of the product you purchase from china.
there is no quality control. so its a good idea to purchase a bit more than you need.

stores i found that supply good quality products from aliexpress: triangelab, Biqu and fysetc.

[dc42]

To get a short from the heater voltage to Vssa there are usually two faults. The first is a short between the thermistor wire and the hot end metalwork, which you have found. The second is a short between a heater wire and the hot end metalwork. So check the heater wires where they come out of the cartridge. If you can't find a short, then there may be a short in the heater cartridge between the element and the case.