I have completed the build of the Arduheater.
I made a connector with led indicator for the 12V. But when i put the USB arduino to the computer the led indicator is turned on.
So somehow the usb is feeding the 12V connector. That can not be right. Futher i'am still waiting for the NTC sensor, so the are not connected at this time. Can this be causing this? How do i test if everthing is working? can you give me direction. I have a multimeter to check voltage i you give me directions

With Regards,
Peter