Are license plates being stolen in parking lots so you can be followed?

SOURCE: Replacing Bulb for License Plate on 2001 Buick Park Avenue

Have you tried to see if there is access underneath to that bulb ?

SOURCE: parking lights and license plate lights won't go off

Lacking an owner's manual, we weren't aware that there was a parking light switch on top of the steering wheel when this happened to our car. We had inadvertently switched that on. Did you check that?

SOURCE: Tail Light and License Plate lights stopped working

With light switch on, test the wires leading up to the mentioned lights with a test light(cost about 5 or 6 bucks at wal-mart) that way u can eliminate any corrosion questions and get to the source quicker, if test light indicates that the wire is hot, than check connection areas for any wear and tear and possible carbon corrosion. Check lightbulbs, my license plate light stopped working and wire was hot, but wouldnt turn on due to the housing base, got too dryrotted and wouldnt function propery, had to rig it up, but works now.

SOURCE: tail lights license plate light won't work. all

check the grounds..and check for damaged wires.

SOURCE: Schematic_Diagram 93 lincoln town car tail lights and license plate light.

Sounds like either your wiring from the Light switch is bad or the Light switch itself is bad. Check with your Owners manual to see if the "Parking lights" have a separate fuse.

Your tail and License plate lights would light with either the Headlights or the "Parking" light selected at the switch as would the front parking lights. If all lights except the headlights are out, your problem is closer to the light switch than at the mounting points of each Parking light or License plate light.

This is one case where you will not know if a dead wire off of the switch is dead because of a bad switch or a bad wire. You would have to detach the harness at the switch, test the wire bundle or jump the switch with power to see how it distributes power through the Harness. It will take a lot of time to rule out the switch. It may be cheaper to replace the switch and then work from there.