I purchased a 2006 Mitsubishi Lancer ES and drove it 400 miles the next day. Half of that time was in the dark. Headlights worked fine. I stopped for dinner, and when I started it again the headlights didn’t work. (Highbeams were, and continue to be, fine.) Ever since then, the headlights have worked intermittently. Sometimes they both work, sometimes only one or the other does, and sometimes neither do.
I am interested first & foremost in diagnosing and correcting the problem, of course. But I’d also like to acquire the electrical schematics, as well as doing the work myself if possible. Help with any of these things would be welcome.
Autozone’s website has free repair info, usually including wiring diagrams for major systems. You just have to register an email address and plug in your car’s info. I’ve found the wiring diagrams to be ok - for the lighting system they should be adequate.
You’ll want to have a digital voltmeter. For intermittent problems one of the most common tests is the “wiggle” test - check for voltage and watch what happens to it when you wiggle stuff. I’d just start with the bulb sockets.
Whenever I buy a vehicle I always purchase a service manual to go with it. Sometimes I use Haynes manuals and sometimes I use factory manuals (more expensive, but better).
I suggest you buy a manual for your Lancer. It will have the wiring diagrams and other information you need to help you fix this problem and any others that may come along.
Inexpensive used manuals are available at http://www.Books4Cars.com