Whirlpool side-by-side always on

Hi all,

I have this 6 year old Whirlpool side-by-side American fridge which has been giving me grief for the past 6 months.
It was failing to cool the fridge section which I traced back to the small electrical vent between the freezer and fridge which had become jammed with ice.
It's now maintaining the temperature in the fridge, but the fridge is now running almost continuously. I have placed a meter on the socket and it's burning 2kW per day... According to Whirlpool's website, a similar model should consume approx 1.3kW per day, so the difference isn't way off, but there are only 2.5 of us in the house and it's not like we leave the door open a lot!

Anyhow, is it possible that the system has degassed? If so, can this be replaced or am I looking at a replacement fridge at an excessive cost???