: I had cause to work with one of the senior refrigeration techs in
: town recently while working on an art project (3 frozen heads in
: Perspex display cases, but that's another story) and mentioned
: it to him. He said it's a fairly common fault - something to do
: with a 'click out' inside the back of the fridge which will have
: died. He said just look for a new fridge - it's not worth the
: labor cost to fix it.

Defrost heater, defrost timer, plugged drain or restricted air flow. All pretty common and simple repairs. Timers are generally behind the toe kick under the frig. You can turn the knob on it manually, you'll here gears, keep advancing it until a louder click at which time the compressor will stop running and the heater in the freezer should come on and start melting the frost in the freezer coils. It all melts, and drains down a tube usually on the back of the frig and into a pan under the frig. If the melting starts, the heater is good. If it melts and does not drip into the pan, check for a plugged drain. If all seems to be working it may be the timer is not advancing by itself and needs replacing.