The high beam does not work?

All headlights were originally fine, then high beams started flickering while going over bumps, and finally quit entirely when pulling into the driveway (moderate bump). The low beam and flash work (flash works both with headlights on and off, as it should). All wires, relays, fuses connectors and two separate grounding connections checked with continuity checker. Headlight switch and dimmer switch also test good with continuity checker. The dealer "recommends changing dimmer switch", but has not examined car, and seems reluctant to take on this problem. Had I not already tested the dimmer switch with the VOM, I would have concurred based on the schematic (Haynes Repair Manual) alone, but if wrong, that is an $84.00 mistake. Recommendations?