I am an absolute electrical idiot. I recently rebuilt my engine. I also rewired the car from the firewall back. I am having a problem that I cannot figure out. For some reason, my headlights will work if the ignition key is turned however it will not work if the engine is started. Other than replacing all the fuses, I did not think that I did anything that should affect the headlights. Please help!

my _guess_ is that you have a ground floating.

When the engine (alternator...) is off your headlights are finding a ground through some weird path. When the alternator is supplying charging current, it is energizing whatever component was allowing current to flow through it previously.

Are your headlights working really well, or is it just a vague glow?

Highbeams and low beams both affected the same ?

You may have to resort to tracing through the wiring diagram, but first, find and clean the headlight ground points really well (from the 'it couldn't hurt' file...)

Make sure you have the transmission ground strap installed!

Could be an ignition switch problem. The headlights get power thru the "X" contact in the switch which has power in the on postion but not while cranking. After starting try turning the switch slightly to off and see if the lights work.