My 84 Westy, original wiring, with H4 bulbs (normal 55w range), has
developed a "dim" drivers side light on low beam.

Not that noticeable, but obviously dimmer.  The high-beam seems equal.

Last time I changed bulbs, I used Di-Electric grease and the contacts
appeared clean.

Any suggestions as to why the one bulb would be dimmer than the other?

Thanks,

Jack R.

84 Westy Wolfie

Bloomfield Hills, MI