Problem replacing fuse 15 blue AMP in Ford Fiesta 1999 ?

Hi I have a red 3 door Ford Fiesta Finesse 1999 I have a problem with my clock and car temperature - seems to be boiling hot even when it's on cold. I've checked the fuse and it's a 15 blue AMP under the hatch by the steering wheel. I have the fuses and I know how to change it but Everytime I try to replace the fuse it blows straight up and it's done without pushing it straight in. Any reason why it keeps blowing up straight away ? I would appreciate it thanks.

Hayley
April 2011