My Tricky Thermistor and Bad Bed leveling

[jmargush]

I have just recently upgraded my v2 to the HE280 hotend and every now and then the temp readout will say 190c when it's cool. Do I have my polarity messed up with my Thermistor? Also, when I run the calibration script it runs fine and when it says it save and I go to print something it's not level. Should have I specified it as a v3 machine when I updated the firmware? Thanks.

Update: Just turned on my machine and the temp readout was 240c

[Burley]

Thermistors are not polarized. It is a 'backward' resistor, the resistance of the device is inversely proportional to it's temperature. As it heats up, the resistance goes toward zero ohms. (It never gets there).

I had a few screws a little too tight, and it moved one edge of the bed up 20-30 thousandths off. Eyeball it, and see if it's mechanically level around the edges.

Jim

[Polygonhell]

It's likely you have the thermistor leads touching something, could be either each other, or a power lead.