well, i'm not sure where to turn here...my left low beam went out on the truck AND the plow last night in the middle of my route, and i've gone through the entire harness and cant fine any loose wires, bad connections, corrosion ANYWHERE. All high beams work fine. This happened before and somehow fixed itself before i could evem look at it...that was 2 years ago. Both bulbs look good tonthe naked eye...help?!