Samsung RS20CCMS1/XEU. Wont Cool. Iced up. For the 2nd time. Plz Help.

[Maz83x]

Hi
Approx 4 weeks ago the freezer wouldn't freeze anything and was iced up from the vent at the bottom. I thawed it and took off that panel (there are 2, i took out the lower one) and with a hairdryer i defrosted it. then i put everything back together and in approx 8 hours everything was cool and frozen again.
3 days ago it happened again. the vent at the bottom is iced up. this time round the fridge isn't cooling either.
i took off both panels this time and before i took the wire off (attached to fan and fridge) i switched the fridge back on and the fan wouldn't move (how long does it take for it to start working? because i literally had the power on for 3-5 seconds).
Also approx 4 inches below where the fan sits it seems as though something was 'blown' as its burnt.
i have attached the photo's.
I also took off the panel at the back of the fridge and brushed off all the dust.
It is not under warranty anymore

[tonto33]

u need to chane the sensor from white to black check the defrost heater and thermal fuse, put into error code mode then force defrost and check heaters etc

[spimps]

Fan doesn't kick in until -10c reached on evaporator so can be 10 minutes or so.

[tonto33]

just replace the heater job done