VT9 thermostat connections?

I want to fit a new VT9 thermostat to my Proline fridge freezer. I have to connect three coloured wires on the appliance, plus the earth to the new thermostat but am unsure which colour wire to connect to each of the three new terminals. The pattern of the three connections on the new thermostat is similar to the old thermostat but the conections are not marked with any symbols. how can I ensure to connect the right wires?