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As per the subject my printer is showing this error in Mattercontrol and the LCD displays:-

NOZ: def
BED: def

I have metered the resistance across the 2 thermistor plugs at the Rambo board end and they both measure 145k ohms so I'd say they are ok.

I know the hotend thermistor is ok and working because I can run the PID autotune, it completes without error, its just the LCD display doesn't report the temperature, just stuck on NOZ: def the whole time.

Can anyone help me troubleshoot this?

What is sounds like is that it is quite cold where you are, as the thermistor is supposed to read ~100K at room temperature, and that you're hitting 18 (As measured by the thermistors), which is the low temp cut-out in the firmware.

Ah thanks! that makes sense, I have the printer setup in my loft, and its really cold up here right now, probably the coldest its been this autumn so far, I guess I'll need to explore making some kind of heated enclosure, damn!

Out of curiosity what gain i say there to continue to move the head about after a hardware failure? is there a way to disable this so that the printer just stops? A month ago i had an issue with this where i was printing overnight and each morning the printer was still moving but no filament was coming out... i thought it was a jam, but nope, my connector from the accelerometer board was loosing causing the printer to go into dry mode... i kind of feel that that is the most useless feature ever.

Some also use an external heat source to initially heat the thermistors above the error threshold.

Some also use an external heat source to initially heat the thermistors above the error threshold.

I did just that, I placed my hand on the centre of the bed just so it warmed from 16ºc to 19ºc and I set the hotend to autotune to heat that up, switched the printer off and on again and bingo we're back in business!

If anyone else gets the same error, before the LCD reverts to def it briefly shows the current thermistor temps, mine were showing as 16ºc so just under the lower limit.

You could adjust

#define MIN_DEFECT_TEMPERATURE 18

to a little bit lower value in the firmware. The trick with the hands won't be needed anymore afterwards.

Thank god for this thread. I just spent the last 4 hours tearing apart and checking every single piece of my Eris to find the wiring fault that I thought was causing this issue. It turns out that my printer was working fine and the reading of 17.2C room temperature was simply too low. I changed the min error defect temp down to 12C, because 18 is a bit ridiculous. I keep my house around 16C all winter unless I have guests.