We currently have this same problem on our 88 Westy.  When we hold the dimmer switch up to keep the headlights on, ours only goes to bright lights.  Just yesterday, my husband resolved the problem by replacing the headlight switch from our other 88 van.  Now we need a new headlight switch - where is the best place (cheapest) to buy one?  Looks like they're close to $30 most places.

Bob & Sharon Mendonca