I assembled the two nozzle version of the vellemann k8400 (kit 8402) - used for a few double colors printings - the second nozzle heated up (at least with simply3d software) every time it was asked to so far
Last print (two colors) ended with a failure: I found the machine stuck in the middle of a layer no moving - the first nozzle set to the target temperature, the second nozzle (to the left) unable to reach the assigned temperature. Now I can use the machine as a single head… the second head won’t heat up: the lcd screen correctly shows the assigned temperature but keeps not heating: the nozzle is realy cold (tested with the finger) but the temperature does not rise. I measured the voltage on the heater cartridge end and it is 0 V: no current.
Did you experience a thing like this? Could you suggest a solution?