Quote Originally Posted by etlsport View Post
low beam operation
When the lighting switch in HEAD and the dimmer/passing switch in LO, the lighting switch provides a ground path to the headlight relay and the dimmer/passing switch provides a ground path for the lo beam filaments. The headlight relay energizes and provides battery voltage to the headlights and the lo beams light up.

Hi Beam Operation
With the lighting switch in HEAD and the dimmer/passing switch in nhi, the lighting switch provides a ground to the headlight relay and the dimmer/passing switch provides a ground path for the high beam filaments. The headlight relay energizes and provides battery voltage to the headlights and the hi beams light up.
heres a blurb on the operation of the headlights from the electrical troubleshooting manual

so it sounds like if the lo beam works and hi beam doesnt, it would be a ground path if its not the bulb