D21s don't have headlight relays from the factory - as a result the stalk switch has to handle all the current for the headlights, and they tend to go after a while.
Never heard of one staying on though! Something must have melted inside it.
See if you can get a cheap aftermarket stalk too, rather than a wreckers. Wreckers ones will also be aged and worn. It's a reasonably common problem.