The bed temperature indicate a value over 250° temp

Jean Michel

I think i've got a problem with the thermistor of the warming bed because i can read 270 degrees (while the bed is at room temperature)
How can i test the resistor ?
Where can i buy a new one ?
The problem is due to after i replace the hotend nozzle, i put a more height nozzle without paying attention, and when i selected HOME, the nozzle push the bed too lower, and i could see a spark on the bed.
After that i discover the temperature problem, and also a driver out of order. I ordered TMC2208 to replace all the drivers.
Now the printer is ready to print, but I am stuck because of the temperature sensor.

Stephen Todd

The thermistor can be tested with a multi-meter from the input plugs - you should get a reading of 100k ohm at 20c, and fall in resistance if you heat it with a hair drier

The thermistor is likely to be OK, and the analogue sensing input pin of the processor blown

The hot end and bed thermistors are identical items - 100k NTC - so you could swap the leads where they plug into the board and see if you now get 270c on the hot end, and 20c on the bed - which would be a blown bed thermistor

There is an unused thermistor port you could use - but you have to edit the firmware to use that instead of the assigned port - instructions are in the wiki

Good news is that the controller board for A5 and A3s V1 is makerbase MKS Gen_L and are dirt cheap - £12 on aliexpress and £20 on Amazon

PS. 270c could indicate melted wiring or melted connector - check the wires are OK with multimeter

Samuel Pinches

Thanks @Stephen Todd

https://jgaurorawiki.com/a5/faulty-temperature-readings

Solution is as Stephen described. I understand you are already looking into it.