The reason I ask is because when I bought my AE86 the headlight switch was doing exactly the same thing. If you know how to use a soldering iron, it is fairly easy to fix yourself. Just pull the switch out and pull the back cover off. Have a look at the solder points and you will probably find one has come away from the board. Just re-solder it and it should work fine. I did mine over 5 years ago and haven't had a problem since.
If you want some pictures, let me know as I'll borrow work's digital camera.