Where is the headlight sensor located on 2003 mercury grand marquis?
on 2003 Mercury Grand Marquis

Sometimes they come on, other times no. Sometimes they just go out while driving.

1 answer 2 comments
Try turning on the manual switch to see if that helps.
sometimes yes and sometimes no
Go out on dim/bright or either way? If either way i suspect headlight switch, if only one or the other i suspect dimmer switch.