I did test by switching bed temp with extruder temp and iI do get a reading.
then i tryied a new termistor for a hexagone hotend not suited for the e3dv6 but it did work so
next will be to buy a new  E3D v6 termistor...

i started a print as always,  a 8h print , i ramped up the feed rate at 130 to speed thing up,  (new titan extruder with e3d v6 combo)
nothing unusual printed started up

i did go out on my merry way

4 hours later i return, the printed had stop, and did get to park position.

i was kinda busy, and did not put attention. powered the all thing off and went to bed (was kinda late)

today, i try again same print.

but i have this weerd message

13:25:10.951 : OpenGL version:4.5.0 NVIDIA 364.72
13:25:10.952 : OpenGL extensions:GL_AMD_multi_draw_indirect GL_AMD_seamless_cubemap_per_texture (blablabla....)
13:25:10.952 : OpenGL renderer:GeForce GTX 970/PCIe/SSE2
13:25:10.952 : Using fast VBOs for rendering is possible
13:25:16.865 : FIRMWARE_NAME:Marlin V1; Sprinter/grbl mashup for Printrboard FIRMWARE_URL:http://www.solidoodle.com/how-to-2/how-to-update-firmware/ PROTOCOL_VERSION:1.0 MACHINE_TYPE:Solidoodle_3 EXTRUDER_COUNT:1
13:25:16.865 : echo:Active Extruder: 0

the temp reading on repetier is 0° normaly it's 20-23°
homing work fine Z X and Y axes are fine.

and I can't look at the extruder  cause i get a fatal error if i try.

so how can i test if it 

1 the Extruder stepper that died ?
2 the motherboard that have a problem ?
3 the tesmistor ?
4 the heatblock at the motherboard level ?

thanks you.

I try to swap the Z stepper to the Extruder stepper and I get the same thing.