Extruder temperature at 0 degrees

Hi

My printer suddenly stopped working. The extruder temperature is showing 0 degrees whilst the bed shows normal room temperature. I gather from other discussions that this indicates an open circuit in the extruder thermistor. I measured the resistance across the thermistor and it shows about 100 Kohms. This is when the unit is powered down. I get the same reading when it is powered up as well. Can anyone point me to what else I can check. Many thanks.

WT4

As you stated correctly, there is an open circuit in your Thermistor wiring.

Unplug the thermistor from the controller and measure the wires for continuity.
The ribbon cable is known to fail easily with broken wires.