Intergral LED thermometer false reading but freezer still works

My Electrolux EU2117C freezer has its own thermometer in the form of six green LED's. They should indicate a temperature in range -13C to -26C. The more lights the colder. However no lit led's are showing suggesting it's warmer that -13C. However, I put in a temporary LCD thermometer and it shows all is well at -18C.

Can I repair the original integrated thermometer as this has an alarm (which I had to disconnect) and a red warning led (which is continuously on). The thermometer module also has a lit green LED to show power is on.

Curiously, after a (manual) defrost, two of the green temperature led's do light up on cooling down, but then go off again!

Thanks Jayeff. The compressor does not run all the time, ie the thermostat seems to be working well, it's only the temperature display that's the problem.

My temperature board (Ispracontrol's 08035019) is very similar to the one you found but not exactly the same.

The board shows no burnt-out components, no trace corrosion, no bulging caps, no heat discolouration, no cracked solder. Without a circuit diagram not really sure want to test, other than testing the discrete components.

Shows images of my malfunctioning temperature control board.