If you have a 3rd Gen 4Runner (1996-2002) that no longer lights the dome light when the doors are opened, chances are your door switches are dirty or in need of repair. Luckily, it’s a very easy fix.
Your door switches are located here on the door, right behind the latch plate:
Gently lift up the lower portion of the rubber cover and use a 10mm socket to remove the door switch.
Use a multimeter in continuity check mode to measure for continuity between the spade connector at the back of the switch and the metal mounting tab.
You should see no continuity when the switch is pressed, and good continuity (~0 ohms) when the switch is not pressed down.
The switch completes the ground side of the lighting circuit when it is released, by creating a path for current to flow from the light to the body of the car.
If you don’t measure any continuity, it’s likely your switch is dirty or broken. I was able to restore mine by pulling the rubber cover back and spraying contact cleaner into the swtich, as shown here:
Recheck continuity. If you not have a short between the metal switch body and the spade connector when the switch is released, you’ve fixed the problem! If not, your switch may be too worn to fix and you might need a replacement.
Peter Den Hartog - Blog