Headlight problem 89 Country Squire

If he has a bunch of lights with dimness, the switch itself is the logical place to start, especially if the pigtail connectors are overheated/blackened.
To remove the switch, you have to be a bit of a contortionist. There is a button on the metal plate that the switch housing is attached to. As you begin to pull the switch knob, you press the button (you may have to press it two or three times while pulling on the knob gently), and the knob and actuating rod disengage. Obviously, disconnect the battery, or your headlights will be on. Once you've done that, there's a plastic nut screwed into that metal plate that holds the switch to the panel. Since it's an '89, you may be able to remove the dash trim to access the switch and pigtail once the switch is released from the dash. Installation is in reverse, so gently insert the actuator rod until it snaps in to lock.