whirlpool fridge too cold Flashing d

hello any info would be helpful
service 8586 411 15010 cant find the short modal number so hope that will do

ok well the freezer works fine but the fridge is far too cold -5 last night and the alarm is going with a flashing d every now and then.

I dont know much about domestic appliances but I’ve had a look and come to the conclusion that the fridge is cooled by cold air from the freezer through a little motorised vent at the top of the fridge which is open even when i would expect it to be closed should this spring return with one of the poles being a switch contact or is it motor open and closed? is this even my problem?
Thanks in advance for any info