I have a 1999 Volvo S80. The main interior light will not come on, either via the switch, or the door/key activation. The remaining interior lights work as they should, coming on as they should, and dimming off as they should. This includes the two small map light on either side of the non-functioning main light. I checked the two bulbs, and the filiments are fine, hence I would imagine they are ok. There is a small green “pilot” light in the switch housing for the main light, and the two map lights. (noted when I pulled out the three overhead push buttons.) All three lights are lit.
It sounds like power is getting to the bulb. I assume the light is turned on by a switched ground connection. I would check the switch operation using a test light probe.
This should be easy for someone with a meter and a little knowledge of how that light is wired.There isn’t any power to the two “main” lights in the housing, but there is power to the two “map” lights in the same housing???