In my case it was a short circuit bulb in the number plate light - fuse F7. Sorry it's 5 years too late.
Keith Lewis, April 2010
What you need
A neon circuit tester or the small relatively inexpensive voltmeters if you know how to use one.
A couple of 10amp fuses.
side light bulbs back and front.
Elec faults are b.....s Taken from a Ford workshop manual
Testing for a short circuit which by the sound of it you've got.
1. Remove the loads ie both the back and front side light bulbs (of course only on the offside in your case}
2. Remove the 10amp fuse.
3, Put the tester on the fuse connection in the fuse box
[One probe in one side the other probe in the otherside of the fuse connections]
4. Switch on the lights and if the tester lights up or the voltmeter reads current this indicates a short circuit.
5. If no light or reading shows then turn off the light switch replace the bulbs and fuse, then turn on the switch if it blows again there is a fault in one of the components ie bulbs.
If you don't feel you can do this or the fault still exists then I am afraid it's an auto electricians job.
