Mr Pounder Esquire wrote:


If you can, take the cover off the evaporator plate and see if it is all
frozen up inside. If it is, the timer could be the fault. Maybe.
There should be/might be little white plastic plugs holding the cover in
place.


The evaporator seems to be just tubes and fins with air blown through. I
have a hunch that my hot air defrosting is just melting a little ice
which then drips down onto other ice and freezes again.

I'll try looking at the control board again. It has a couple of triacs
on it and I suspect they switch the fan and the heater.

If I can be certain which is the defrost heater, I might be able to
power that up manually, leave the freezer loaded but switched off and
accelerate the defrost process? Worth a go I reckon.

Bob