Best posts made by wkellyo

My newly ordered filastruder Duet2 board came in yesterday and I decided to install it today. I just knew it was going to fix my issue. I installed the new firmware, Got it connected to WiFi and traded my SD card with the one that came, hooked it all up and flipped the switch and.... DARN!! Same thing - Bed Temp fluctuating all over the place (within about 10c) So, I deducted my clone duet board was fine. Bright side: I now have a matching OEM Duet and Duex! I defiantly decided I was going to unplug every plug on the board, one at a time until I found the issue! As a test which I did several days before and it didn't make a difference, I connected another thermistor and left it hanging to the floor. The temp was perfectly stable. So, I began stripping the wires from the bed out of the wiring ducts with the fluctuating thermistor connected back up. nothing seemed to change it. I might mention I'm using a 120v silicone bed heater. I checked the thermistor to the bed for any stray voltage and found about 0.126 vac on the thermistor so I figured maybe some some inductance was going on but could never find it even after disconnecting most of the 120v bed wiring, I never disconnected the neutral from the bed heater. I also found about 4-6 vac between the bed heater frame and the earth ground. The bed frame is mounted in a kinematic setup so it floats on three points which the three bed leveling steppers are driving. I broke out the meter and started testing stuff. The bed frame is isolated as the meter showed infinity ohms from the bed frame to ground so I'm not sure where the stray voltage was coming from. I decided to try grounding the bed heater frame to ground and the temp stabilized perfectly. After the test, I ran a permanent ground to the bed frame, put it all back together and that fixed my issue. I plan to run grounds from all seven steppers as well since they are all mounting in plastic and add a few more here and there for good measure.
Hope this helps someone else.

1RI, thank you so much for the information, I figured there was a way that even I could understand, this really helps a lot and I even have a few ESP32's laying around besides Nano's, Unos and even a few Mega Arduino's.