On my `95 yamaha timberwolf I'm having some problems with the headlights.

There are two settings on the lights but I'm not sure why, they appear to do absolutely nothing when going from the low stage to the high. Is it a brightness selector? There is only one bulb in each headlight so I'm not sure how it could be high and low beams.

Now onto the real problem...sometimes when I turn on the headlights only one light comes on. Then when I go from the low to high setting that light shuts off and the other one comes on. Then if I drive around for a while both come on? All the wiring appears to be correct based on the clymer manual.