Bed H0 reads 2000*C ! Sensor Open Circuit FAULT Test 4 Fuse ?



  • New Duet Wifi Install …

    Hot End Heats and reads temps just fine ...

    Bed circuitry appears to have pooped the sheets

    Bed H0 - reads 2000* C - Faults on PID Auto tune attempts - "Sensor Open Circuit." - or just Activating it . rechecked wiring - re crimped the thermistor ends 2x. They are fine. Silicon Heated Bed with NTC 3950 thermistor. Plugged in 2 spare thermistors I had in my spares bin - same error.

    Bed worked fine on ramps ... very good actually. Multimeter reads 118k Ohm on bare wire ends and with crimps on.

    Read forums appears other issue may be Popped Fuse? WTH ? Handled this thing with "kid gloves" so far ...

    Have no clue if those settings in the following section are accurate for the NTC 3950 thermist ... I punted on the configurator and it spit those out.

    Here's my heaters section:

    ; Heaters
    M301 H0 S1.00 P10 I0.1 D200 T0.4 W180 B0 ; Use PID on bed heater (may require further tuning)
    M305 P0 T10000 B3988 C0 R4700 ; Set thermistor + ADC parameters for heater 0
    M143 H0 S70 ; Set temperature limit for heater 0 to 70C
    M305 P1 T100000 B4725 C7.060000e-8 R4700 ; Set thermistor + ADC parameters for heater 1
    M143 H1 S265 ; Set temperature limit for heater 1 to 265C

    Not sure what else to try … wits end and all ... Is there a way to remap this to another heater / thermistor PIN set ? Im using a DC/DC External Mofset - which again works flawlessly on RAMPs 3 days ago



  • I have reversed the thermistors between E0 and H0 and the spare on on E0 - to test its efficacy.

    Heatbed thermistor read 21-22C when plugged into the Extruders E0 Therm onboard connector - same for the Spare 100k Therm

    H0 / Heatbed connector reads 2000*C regardless of what Therm is attached to it …


  • administrators

    Your M305 P0 command is for a 10K thermistor (T10000) but you have a 100K thermistor.



  • @dc42:

    Your M305 P0 command is for a 10K thermistor (T10000) but you have a 100K thermistor.

    well that was famously embarrassing … TY ...

    Let that be a lesson to ye kidz ... stay in school ... reading comprehension, and working on tiny connectors and reading small print tutorials off the web till yer eyes twitch - may cause you to make silly mistakes ...

    Changed the T values for that heater H0 ... and viola' - room temp is reading at 21*C on cold bed [ H0 ]


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