[Tommy]

I offer these suggestions in spite of the fact that I know absolutely nothing about how your car is wired, so take them with a big grain of salt.

First, run a jumper cable from the headlight ground to a known good ground, and test the lights. If they still don't work, it's not the ground.

Second, use your continuity tester to see if power is getting to the light switch. If it is, check that it leaving the switch when it is ON. Then follow the power until you find where it stops. This is not as easy as it sounds. ... Also be on the lookout for a relay (typically four wires connected to it). It could be the problem.