If all other lights work then it is obviously not the in-line fuse.
My guess is its much the same prob I had [one side light and one indicator], a bad connection at both the c/van plug and bulb holders. Clean up the c/van road light plug terminals pins and sockets then check if all works if not then remove bulbs and clean both bulbs and holder terminals. There is a electric terminal cleaner, I think its called Triflow there is controversy about using WD40 in caravan club mag so don't use it. You can use a white grease spray [vaseline] which doesn't cause resistance and is used on battery terminals. Go to a car shop or C/van accessories if near you and explain what you want then you'll get the right stuff.
nobby, April 2008