Proof of concept for modifying the map lights to work with the dome light. This is for a 1999 Toyota 4runner Limited with the sunroof. Non sunroof models have different wiring.
This circuit uses the ground switch on the dome light to activate a relay which powers the map light bulbs.
The dome light is ground switched meaning it always has 12V available and the light comes on when ground is introduced. That is either by grounding locally via the "ON" position of the dome light OR grounding via the door switch circuit in the "DOOR" position.
The map lights are power switched meaning that the bulb is always connected to ground and the light comes on when power is introduced. This normally happens via the on/off switch. Adding the relay allows it to get power in conjunction with the dome light. I added (2) relays because I still want to be able to operate the map lights independently.
