4wd not working

[mik]

hiya cant get 4wd to work suspect somethings stuck or just a relay not working does any one no where the add unit is situated ?found a vacume pipe off the back of transfer box but made no difference are the relays in the foot well drivers side the ones for 4wd ?any other ideas or where i can test for power ?what usually stops 4wd working is there a fuse for it ??