The left front headlight does not work. I suspected the bulb but it lights when attached to 12 v. The right side works and the fuses are good. Wiring looks good. A couple times at night it has popped on for a couple miles then died out again. I can't even see how this could happen when looking at the wiring schematic. Any ideas?

 

Sounds like a possible loose connection in the wiring / plug somewhere, at least if it pops on and off every so often. Would have to backtrack through and see if you can figure out where though, I don't have much experience personally with the circuit, but just at a glance it sounds like something not making a good connection.

 

Do the other lights on that side work? If not, check the ground. If they work, loose wire. Either way, examine the fuses.