No power to hot end heater

I have spent the last week assembling and commissioning my Ormerod and have printed 3 sets of axis compensation test pieces the last one being yesterday with no problems. I just sent my first proper print to the machine when I found it taking a long time to start printing.

After about 10 minutes of waiting I realised that the bed had reached temperature (57 deg) but the hot end was still showing room temperature. Confirmed with finger that hot end was still at toom temperature (21 deg). Probed with a multimeter and confirmed that there was no voltage across the hot end heater. Traced wiring back to Duet board and still no voltage on heater lines. Reset and restart, still nothing.

All other functions work as they should when controlled through Pronterface.

I am at at a loss about what to do about this.

Any ideas?

Thanks.

Update: Tried again after 30 min of doing nothing. Now works.
Will update if it happens again.

Update: Problem is back.

No control of hot end from Pronterface. All other controls work including control of bed temperature.

However sending a supplied gcode (snowman, coathook) reactivaates the hot end and object prints fine. Sending a gcode made by Slic3r does not work: printer stuck at waiting for hot end temperature to be reached. Hot end remains cold.

could it possibly be a faulty thermistor ? try switching the thermistor wires for the heatbed to the hot end and see if the problem persists

Well.

Perhaps it could have been, although it has been working fine for the last few days. The issue with the freeze on print start turned out to be a retraction speed of 60mm/s causing the machine to wait indefinitely at the start of the print. Setting Slic3r to max 30mm/s retraction speed has solved that seemingly separate problem.