My Small Transformer

this is my homemade transformer..i mean small...
its a transformer from a rc car charger...
i use ac adapter 12v...
i winding the primary coil(input)5 turn and in secondary coil(output)20 turn...
it is a e_block transformer...
i use ac adapter 12v as the input voltage...
i use 18v small pc fann...
its doesnt workk!!!!1
but why???
i hope u guys can help me solve thiss...
thanx you.....
one more...i want to make step up transformer.....
help me....