SOLVED!!! Found the failure... overseen, that i changed with M307 also P0 and P1.... canceled the two lines and now working like a charme!

@veti yes I'm aware of this, anyway thanks for the input

now I've found time again to solve the PT100 issue. Still the same situation showing up 2000C... All double checked again and went through all forum.
Firmware: Just updated today from 2.02 to 2.03 latest RC => no change
config.g attached (without some details)
Devices:
P0 => general temperature measurement up to 80°C (2-wire, with conbectors on X205)
P1 => Heatbed sensor (4-wire, without connectors on X204)

0_1561986375097_config.g

When resending all seems to be fine. In webinterface it is green and i my console I get an OK.

No, nothing connected on that interfaces. Actually only the Mini USB and Ethernet. Mini USB is for receiving G Codes and ethernet only for maintenance reasons...

Duet Ethernet
Duex5
Daughterboard PT100 connected on Duex5 (but also tried on Duet itself)
Channel 1: 2 wire PT100 with jumpers installed
Channel 2 4 wire PT100 without jumpers

Both sensors measure 108.9 ohm

Changed in config.g
M305 P0 X204
M305 P1 X205

Also tried with 100 ohm resistor (with jumpers) on both channels.
Also gave a try to do it on Duet mainboard with X200/X201

All with the same result: 2000°C...

Also tried two brand new PT100 daughterboards (V1.1) - nothing changed...

Any ideas???

Working pefect! Definetly solved! Thanks

so you are switching the "minus" on the board, correct? we bridged it because we do have a valve isle with a common ground. now the lucky thing is, that the valves mounted are in a "unpolar" execution, so we can wire it that it will be correct... don't worry about the diodes shown in schematics, already mounted them the correct way

The valves are connected with a common ground (24V). Here the schematics and a picture. When I send the command M42 P2 S255 all onboard LED are going on and the valves are acting.

Not working with conifg-overwrite.g file yet, so there is no such file. Sent commands via YAT directly. Planned is to code it directly into config.g file as soon as it will work.