Beko AB910 not working. How do I fix it?

We have had a Beko AB910 for a few years and up until recently it worked well. A few weeks ago, it started acting up, not working on the top and freezing a layer of ice down on the bottom. We got a replacement fan for it but it works for a few seconds and then stops. Is this meant to happen? And if not, does anyone know what's wrong?
Thanks.