Bed thermistor give me wrong value

e4d

Hello, the thermistor of the heated bed give me really strange values. I don't put the heater on and it goes from 200°C to 450°C and it vary a lot.
I checked the resistance with a multimeter and it's around 98k at 25°C ambiant temperature. It's connected to "TEMP 0" input on my Duet 3 Standalone. I don't think the problem is the wiring as if I'm correct the thermistor is not polarized.

Here's the config for this part :

; HEATERS
; H0 Bed
M308 S0 P"0.temp0" Y"thermistor" A"Bed" T100000 B4138 C0    ; configure sensor 0 as thermistor on pin temp0
M950 H0 C"0.out0" T0                                        ; create bed heater output on out0 and map it to sensor 0
M307 H0 B1 S1.00                                            ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0                                                     ; map heated bed to heater 0
M143 H0 S120                                                ; set temperature limit for heater 0 to 120C

It seems correct to me but maybe I'm wrong.

PaulHew

@e4d said in Bed thermistor give me wrong value:

M308 S0 P"0.temp0" Y"thermistor" A"Bed" T100000 B4138 C0 ; configure sensor 0 as thermistor on pin temp0

Instead of 0.temp0, change it to temp0
and the same with out0

Just a suggestion.

P.

jay_s_uk

@paulhew that doesn't matter. both can be used.

@e4d do you actually know what thermistors you have? they probably won't be B4138's

dc42

@e4d I suspect there is an intermittent short circuit between one of the thermistor wires and something else, perhaps the hot end metalwork.

e4d

@dc42 this is the problem, thank you. I will try to repair it