glow worm fuelsaver 80 f keeps blowing its 1 Amp fuse?

I have a glow worm fuelsaver 80 f ..and when I switch it on the 1 amp fuse in the circuit board will blow instantly..there is a fan connected to the circuit that that is part of the start up process......When I take the out to test if it was working ..I put a 1 amp fuse across it and it would blow ..However if I put a 3 amp across it it runs quite sweetly...I cann't work out if its a 1 amp fan thats worn out and needs 3 amps ..or ...the circuit board is shorting and blowing the fuse or ????something else ...thanks for your help