hotpoint fridge freezer 8496p fridge is warm

Our Hotpoint fridge freezer 8496p fridge is warm. the freezer works fine but the fridge temp varies from 5 to 16 degrees when I checked the evaporator in the freezer compartment it had large blocks of ice around it. Previous posts have indicated that the thermistors need replacing.

Can I verify if both or just 1 needs replacing or is there any information on how best to check and then carry out the replacement.

I have been told to melt the ice in the evaporator with a hair dryer by blowing through the vent in the fridge this would then allow the cold airflow up into the fridge.

Previously the fridge freezer had water collecting in the hollow at the top of the freezer door but it worked ok. This has stopped but the fridge is now getting warm.