Hey guys, just wanted to update here.
I got new parts from E3D and now everything runs smooth again, so it was related to the bearing gate issue.

Thx for the tip with the bearing gate.

Yeah, but I had a few hours of printing after the rebuilt with 3.1.1 without any issues. But I will double check the wiring.

I can try, but I havent had this behaviour before the 3.2 upgrade with the old PID tune. Hotend isnt grounded, you think that could change readings?

@Blacksheep99
Yeah, exactly like Phaedrux told. Just the M308 A Paramter.

I changed the R value as dc42 told me to, and the overshoot is almost gone. There is a small hickup close before reaching the target temperature but nothing special.
Here is the curve:

Thx for the explanation. I will adjust the R parameter like you said and see if that helps with the overshoot.
I will have a closer look at the spiky temperature at the heatup phase, maybe it was just a hickup.

Cableing should be okay, I just rebuild the printer and redid the wiring with new cables and crimps. Could any config related stuff interfere with the temperature readings?

I've just updated to version 3.2 coming from 3.1.1 and also did the new PID tuning, using the tool as "heater" M303 T0 S240. Everything went okay so far, but the results arent that good.
This was the first print I did, it really took some time to get stable temps (there is a 5 degree drop after the first layer via slicer):

In another print I've got a heater error and a quite spicky graph, forgot to make a screenshoot of it. Cleared the heater fault afterwards and restarted print, which went fine.

This way my old PID tune with RRF 3.1.1:

M307 H1 A735.3 C254.6 D5.2 S1.00 V24.2 B0 

And new with 3.2

M307 H1 R2.576 C273.2:173.4 D5.89 S1.00 V24.3

Any ideas what could be the issue?

I already tried other P values like 0 or 1. But it doesnt change a thing, the current config check response is this:

M98 P"config.g"
RepRap name: My Duet
TELNET is disabled
Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 651C

And this is the current code:

;DUAL THERMISTOR SETUP for bed
M308 S0 P"exp.thermistor3" Y"thermistor" T100000 B3950 A"Bed Pad"   ; configure sensor 0 as thermistor on pin bedtemp (pad sensor)
M308 S2 P"bedtemp" Y"thermistor" T100000 B3950 A"Bed Plate"  ; configure sensor 2 as thermistor on pin e1temp (plate sensor)
M950 H0 C"bedheat" T2 Q10                                   ; create bed heater output on out0 and map it to sensor 2 (plate sensor). Set PWM frequency to 10Hz
M143 H0 P0 T0 A2 S40                                  ; Regulate(A2) bed heater (H0) to have pad sensor below 110°C. Use Heater monitor 100 for it
M143 H0 P0 T0 A1 S50                                  ; Shut off (A1) bed heater (H0) if pad sensor exceeds 120°C. Use Heater monitor 101 for it
M143 H0 S120                                                ; Set bed heater max temperature to 120°C
M140 H0                                                  ; Mark heater H0 as bed heater (for DWC)

I already tried to alter them and get rid of the X commands, but still doesnt work:

;DUAL THERMISTOR SETUP for bed
M308 S0 P"exp.thermistor3" Y"thermistor" T100000 B3950 A"Bed Pad"   ; configure sensor 0 as thermistor on pin bedtemp (pad sensor)
M308 S2 P"bedtemp" Y"thermistor" T100000 B3950 A"Bed Plate"  ; configure sensor 2 as thermistor on pin e1temp (plate sensor)
M950 H0 C"bedheat" T2 Q10                                   ; create bed heater output on out0 and map it to sensor 2 (plate sensor). Set PWM frequency to 10Hz
M143 H0 P100 T0 A2 S40                                  ; Regulate(A2) bed heater (H0) to have pad sensor below 110°C. Use Heater monitor 100 for it
M143 H0 P101 T0 A1 S50                                  ; Shut off (A1) bed heater (H0) if pad sensor exceeds 120°C. Use Heater monitor 101 for it
M143 H0 S120                                                ; Set bed heater max temperature to 120°C
M140 H0                                                  ; Mark heater H0 as bed heater (for DWC)

Can you tell me where exactly is the fault?

What I dont really get what the P parameter means. What is a heater monitor? I have to admit that the documentation is very cryptic for the whole new rrf3 stuff.
I also tried other parameters like P0 or P1, but the M143 settings are completely being ignored no matter what I do. I even changed the order of the commands and deleted the M143 H0 S120 command.

I just can't get that working on rrf3. Tried different options for few hours but heater does ignore the M143 commands.
Why isnt this working in rrf3? I really dont want to get back to the "old" slow heating method.

Hello guys,

I 'm in the middle of upgrading my duet 2 wifi to rrf3.
Think most of the conversion is done, but I struggle a bit with my dual thermistor setup.
I've got silicon heater mat with its thermistor and I got a second thermistor drilled into the heatbed itself.

For the rrf2 I got a dual thermistor setup working. So that the silicon mat could go to max 130 celsius if the bed temp isnt reached yet. This allowed for faster heating. But now I cant get it working. The "virtual" sensor for controling the silicon heater doesnt work. It doesnt shutdown when the max temp is reached. It just stops when the heatbed thermistor has reached the limit.

Maybe someone could help me. This was the code in rrf2:

;DUAL THERMISTOR SETUP
M305 S"Printbed" P0 X0 R4700 T100000 B4276
M307 H0 B0 S1                    ; PWM (B1 = bang-bang)
M305 S"Heatmat" P103 X3 R4700 T100000 B3950
M143 P100 H0 X103 A2 C0 S123            ; supervise silicone heater stays below 123°C
M143 P101 H0 X103 A1 C0 S130            ; supervise silicone heater shutdown at 130°C
M143 H0 S115                    ; maximum heatbed temperature

and this is what I got so far for rff3

;DUAL THERMISTOR SETUP for bed
;Bed
M308 S0 P"bedtemp" Y"thermistor" R4700 T100000 B4276
;Heatmat
M308 S1 P"exp.thermistor3" Y"thermistor" R4700 T100000 B3950
M950 H0 C"bedheat" T0
M143 P1 H0 X1 A2 C0 S123            ; supervise silicone heater stays below 123°C
M143 P1 H0 X1 A1 C0 S130            ; supervise silicone heater shutdown at 130°C
M143 H0 S120                    ; maximum heatbed temperature
M140 H0

Thx for the clarification. Like I said, I already got it working in S3D.
These are the settings I'm currently using:
M207 S4.5 R-0.05 F4800 T1800 Z0.20

But now it also works with Slic3r. Just used the newest beta version of Slic3r PE instead of the stable release.