electrical fault headlights OR wipers

i have an o2 plate freelander that has developed a wiring fault, i can either use the headlights OR the window wipers if i use both the fuse blows an only the wipers stop working, i have changed the headlights stalk an gone thro' a dozen fuses, this is now driving me mad as i cant find why it's shorting out, any ideas as to why this is happening wud be gratefully recieved
...thank you