a few weeks ago the nearside headlight blew so i bought a pair of replacements and changed it. no problem! on friday the offside headlight was out so i changed it at work this morning with the other bulb, still not working. i have been out and bought another set just in case it was a duff bulb. still not working! im assuming they both run off one fuse which rules that out so what else would cause one lamp to fail?