First, clean up all the connections in the headlight circuit, then check the voltage at the battery posts (NOT the cable clamps) with the engine running at a fast idle. It should be around 7.5 volts against a fully-charged battery. (Charging the battery before doing any adjusting is VERY important). If the voltage is low, turn the Phillips-head adjusting screw on the right hand coil in your picture clockwise a little at a time to raise the voltage. DO NOT mess with the other adjustments. Before doing any adjusting, disconnect a battery cable and scrub a clean piece of business card stock or a slice or a file card between all the points in the regulator.. DO NOT use a file of any kind, or sandpaper on the points.

Be aware that the voltage regulator setting will drop slightly when the regulator cover is reinstalled- - - -steel conducts magnetism better than air does- - - -so set the voltage regulator a tenth of a volt or a little more higher than the final setting you want.

Now, once the charging system is adjusted, try fixing the real problem- - - - it's most likely corroded contacts in the dimmer switch.
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!