What causes my low-beam headlights to work only in daylight, not after dark?

Yes, that is correct. Also, normally when I turn on the low-beam headlights, the dash lights dim. That function, too, works perfectly in daylight. As soon as it gets dark out, when I turn the lever to turn on the low-beam headlights, the headlights will not come on, nor will the dash lights dim.

Suspect failed multifunction switch.

Thank you, pushrod. I don't know if I am allowed to ask a second question...If so: exactly WHERE is the multi-function switch located, in a 2008 Pontiac Vibe?