Failing to start print -273.1 bed and non response

Just tried to do my very first print.
All seemed to go OK, temp on hot end and bed reached target, then the axis moved to home, then bed reads -273.1.
Then nothing, no bed movement, nothing responds, no axis movement, Pronterface does not respond, I have to force shutdown program.
Reconnect after a few minutes and the bed temp is back to normal.
Try to print again, and then -273.1 again.
Its only ever had this reading the last two times, its been correct up until now and connecting again makes it read OK.

Any ideas where to start looking for problems? We are sure its not wiring or the thermistor as reconnecting (with no axis or printer movement) gets the reading back to normal.

Had the same when I changed my Y-belt tensioner. The connection to the bed thermistor on the ribbon cable, the one where you stick really thin cable in a crimp end that its not designed for. The pins were no longer clipped in the housing and as the bed moved it put pressure on the connector and just removed the connection. I would start there and work back along cable checking temp is OK in pronterface as you go.

Dan.

I'm sure its not the wiring.
I taped the connector up under the bed, wires well away from rod and belt.
Connected, temp OK.
Heat up bed and hot end OK.
Then with no movement on either axis, the temp then just shot down to -273.
Now its jumped to -46. Still no axis movement.

Does this sound like symptoms of a faulty thermistor?
Or is it really down to bad wiring?

It could just possibly be due to a fault on the Duet board, but bad wiring (especially those thermistor crimp connectors) is far more likely. I recommend soldering the thermistor ends to the crimp connectors. It could also be a bad connection between the 2-pin plug and socket under the bed, especially if the pins and sockets haven't been pushed all the way into the housings.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

OK, as suggested it probably was a connection problem.
Removed plug from Duet, couple of the pins had some plastic residue on, so I scraped it clean.
Also removed the bed, tugged on the wires on plug and socket. Plugged all back in.
And its printing the start of a snowman.
The bed is now not correct, I need to re-do my axis compensation, but hopefully in the morning I can do the proper set up and get the ortho printed off
Thanks all for the suggestions.

its done it again.
Half way through ortho axis print, the thermistor under the bed reads -273, I didn't notice, the bed cooled, one end of the print lifted and the hot end hit it.
Now setting it up to print again, but so far I am not impressed that the thermistor has disconnected again.
I think the bed may have to totally come apart.