I have a 1991 Mercury Grand Marquis. I am having trouble with the parking lights and instrument panel lights. They work some times, but not most of the time. All other lights work, brakes, headlights, 4-way flashers, & turn signal. Any answers?

Sounds like you need to replace the headlight switch. Sometimes they partially go. Looks like yours took out the parking lights as well as the dimmer switch, which is why your interior instrument clusters are dark.