How do you replace the headlight switch in a 1989 Grand Marquis Headlights work but tail lights and dash lights do not tried to remove the dash panel but cannot remove the knob on the switch?

There is a small spring-loaded button on the top of the headlight switch. You'll see the button on your new switch. Press the button while rotating & pulling on the knob and it will slide out. The trick is, it's impossible to reach the headlight switch from underneath the dashboard. I removed the screws holding the fuse block, then pushed the fuse block in toward the front of the car, giving me room to get my hand in to reach the switch and the button.

Remove the dash bezel by removing the four screws from the top underside of the dashboard.

If you pull the old switch out of the wiring connector, you'll probably see at least one of the slots is melted and/or burned. You'll need to replace the wiring connector. Here's a hint: rather than snipping and splicing in the new wiring connector, use a small flat screwdriver blade to remove the wires from the old connector, then snap them into the new connector. You'll probably have to cut & splice the wire from the burned slot, but the rest should be usable in the new connector block.

The whole job took about 2 1/2 hours from beginning to end.