Buy a spray can of electrical contact cleaner, and hose the dimmer switch down with it, then operate the switch repeatedly, lights on or off doesn't matter. Repeat as necessary until things either work right or the switch self-destructs. Something as essential to safety as the headlights deserves a new dimmer switch- - - -sort of cheap life insurance if you plan to drive at night.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!