Wrong Temperature readings

I got problems with my temperature readings.
This is what repetier displays when the cables are plugged in:

notting plugged in:

I checked the termistors values: they both are around 160kohm which is ± 17°.

checked some values on the board

The printer was working correctly last week.
What can I do?

update: links to images:
onedrive.live.com/redir?resid=C … hoto%2cPNG
onedrive.live.com/redir?resid=C … hoto%2cPNG
onedrive.live.com/redir?resid=C … hoto%2cPNG

If repetier shows 0°C it’s likely you have a open circuit in the thermistor wiring or a bad thermistor.

Where and how did you measure the resistances?



I measured the thermistor resistances at the end-plugs with a jumper-wire in them.

Did you disconnect them before taking your measurements?


Isn’t it strange that if i unplug the heated bed (power off/usb off), it stil shows up in repetier at 25°C.?

So, if i get you right only the hotend thermistor doesn’t read correctly?

Yes, both the hot-end and the heated bed.

You get wrong readings on both, in repetier?
Sorry, but i don’t get the point in your pictures, otherwise the hotend showng 0°C.

Yes, hot-end = 0°C ; heated bed = 25°C
room temperature: ±18°C

Could you pleas again explain which readings you get when what is connected?
I’m a bit confused…

even when the cables are not attached the temperatures are around 0°C and 25°C.

If a measure the resistance of the thermistors (at the plugs, disconnected of the board) they are around 160kohm

Ah, ok.

Then unplug the USB and 15V power and measure the resistors near the THERM connectors (the small smd ones)
They should read 4.7 KOhms.

If your printer is not connected repetier can’t show correct temp values, as they are sent by the printer itself.
They simply don’t update if the printer is offline.

Already done: they show up as 4.7 and 7kohm.

Which one shows 7k?

the one of the heated bed.

Strange, it should be 4.7k too.

Does the hotend thermistor show proper readings if connected to the heatbed connector? (THERM2)

no, it reads 25°C. Which is not the correct temperature.

if the heated bed is attached to the thermistor pin is says 0°C

conclusion: if the thermistors are switched, nothing changes.

Can you please measure the voltages across THERM1 and THERM2 please? (nothing connected to it)