Liebherr CN(es)..6 Diagnostics

I have a long standing problem with a CNES3866 Liebherr Fridge Freezer...

Despite having a free flowing pipe in the channel at the bottom of the Fridge section the unit ends up forming a block of ice in the channel and then causes water to accumulate in the base of the fridge section (salad crisper).

The fridge section does not have a defrost. Instead the intent is that the evaporator cools the back wall, potentially causing some frosting and then during a compressor idle this frosting evaporates, drips down to the channel and out of the drainage hole.

I am presuming that the cycle for removing the water formed is not functioning correctly due to a temperature sensing issue of some kind?

The appliance has a Diagnostic mode...

On/Off + SuperFrost (3+ seconds)
Up x 3 => H menu to E menu
SuperFrost

and then you can see the current sensor readings...

E1=Fridge air... I get 5C
E2=Fridge evaporator... I get -16C

E1 seems OK... fridge is set for 4C but that isn't far off.

How do I interpret E2 values? Is -16C a reasonable value?

Thanks in advance
BfW

Hi Brian
I don't know this model of F/F but know the typical function of these units, which are as follows, hopefully it may guide you into whats gone wrong.

The refrigerant in the system goes through the freezer section first where there are a series of evaporator tubes to freeze that section. The gas then leaves the freezer section and enters the fridge section , which is a small roll bond evaporator, that simply chills the fridge area by convection from the evap coil which has a temperature of between minus 15 to minus 25 deg C When the thermostat that is fitted to the fridge evaporator reaches its set temperature the compressor stops . The temperature of the fridge evaporator must rise up to something like plus 3 or 4Deg C so that any frost on the fridge coil melts and drains through the small hole underneath the evaporator and drains into a condensate pan mounted on top of the compressor. Some systems simply use the warm ambient air in a kitchen to raise this temperature and defrost the coil. Some systems have a small heater underneath the fridge evaporator which energises to defrost the evaporator and then terminates around the plus 3 deg c mark.
So it maybe the stat is now faulty , or the heater which looks like a aluminium tube the diameter of a coathanger may be u/s, as it sounds like the compressor is allowed to restart before the fridge evaporator has warmed up to allow the condensate to drain away. Hope that helps you to diagnose the problem E1 & E2 look OK