I have an he3d 600 printer, bought about 2 years ago. It's using repetier host. The printer has two extruders. I have a problem where I can get one extruder to heat up, but the other one doesn't, and neither does the heated bed. The extruder that does heat up will not stop heating and will continue till it reaches up to about 300 C. The repetier host software is showing the temperature readings correctly, but the extruder just continues to heat. I don't believe the other extruder or the heated bed have ever worked for me, but the overheating extruder is a new issue. Any suggestions?
Have you tried changing the termometers? or try to set up a second printer on repetier host with the same configuration, this worked for me a while ago and my last recomendation is for you to try to print from sd card, and discard that the issue is the conection to the pc.