Help, Advice, Owners' Discussion and DIY Tutorials on S40, V40 and V50. In this forum you'll find S40/V40/V50-specific owners asking and answering questions on maintenance, ownership, repairs, tutorials and almost every do-it-yourself thing you can do to save money owning these Volvos. 1996 - 2004 S40 1996 - 2004 V40 2004 - 2004 V50
It is probably the lamp control module. It's the big control unit under the left side dash. They incorporate all the high/low and power relays for the exterior lamps in a single black box on the 40 series. Big bucks to replace.
The box opens easy enough. Inside is a single circuit board chuck full of electronics and a few relays. I think it could be repaired by someone with experience with circuit board repair.The relays themselves look to be pretty generic and I was able to trace it down to one.