Because there are two different bulbs for the hi-beams and lo-beams
This sounds like a direct short my 2001 frontier does that too, i was told it was an electrical malfunction.
yes but you would have to change the clutch
Switch? both headlights?
Headlights have two filaments, one for dim, one for bright. From your description it appears that one of the high beam filaments is burned out. Replace the bulb.
It is safe to use the bright [highbeam] headlights when there is no oncoming traffic/drivers who could be blinded by the bright light. Also, it is unsafe to use highbeams when there is fog or smoke which would reflect the light back to you, thus reducing the distance which you can see.
Check your fuses.
I don't know but i just bought a 2000 Nissan frontier with a leer camper sheel i have the se 4X4 it might not fit yours but if it does i would sell it to you its white Joepeters@insightbb.com
A bad battery or faulty battery connection.
sounds like that would be your clutch wearing out
yes
it might... but you would want to contact your dealer just to be sure.
I know that the ECMs are the same. If the mounts match up I would go for it.