De-lighted ... help required

Does anyone have any 'bright' ideas, please? 1990 Celica has a problem with dipped beam ... sometimes they both work, sometimes only one works and sometimes they don't work at all!

A wiring diagram would be helpful if anyone has one, please!

you have a short, check all fuse connections and use a test light on all the wires, find a wire that dosent repsond and replace