Why is the motor on my fridge/freezer working most of the time?

My secondary (old) fridge seems to have the motor running most of the time. I was about to just change the seals as they do look worn but wonder if it could be something more serious which may not be worth repairing. The fridge works fine, in fact it cools too effectively and sometimes bottles of wine freeze. I have the fridge set at the minimum cooling level. The freezer compartment is below the fridge and it ices up regularly, over a few months. I only use the fridge as a beer and wine cooler and generally do not keep anything in the freezer. The fridge is a Westinghouse RB411G.