how can i fix my banfoss 103 timer switch so i can have heat?

i changed the plug fuse in my timer switch putting a 3amp in when i switched the switch to on it started making a sizzling sound so i changed the fuse to another 1 same thing happened after trying to put the heating on but before i could switch it off it blew ive tried looking up on different sites on the internet for any means of help but not had success i need heat as its really cold have i put the wrong fuse in and need a higher 1 or can this be fixed easily without paying for some1 to come out and fix it please if any1 could help i would appreciate it