OK. Bulbs are good, and the dual filament ones are in the lower outer lamps. Is the white bulb holder in the right side lower outer lamp?

The next thing to check is the condition of the mini-clamps inside the white color connector. The connector is held to the circuit board by a tooth that you can pull a bit upwards while you pull the connector towards the car front.

Look at the connector and you will see the little mini-clamps. Next look at the bottom side of the place where the connector hooks to the circuit board. Takes a mirror and flashlight. You might see that the places where the mini-clamps make contact are burned and/or pitted. Sometimes this works: Clean the circuit board places with a pencil eraser.

The connector can be opened, the back is hinged. It comes easy when you have the right angle, look for little clips on the end of the connector that hold the lid shut. Use needle-nose pliers and carefully remove ONE mini-clamp. Squeeze the jaws together so that the space between the is reduced, not eliminated. Do this for all of them, being careful to get each one back into the same slot. {Put the connector back on and run the "does it light" test again.

If the circuit board contact areas are just too bad, you might get a tiny bit of heavy duty aluminum foil to fold over the board. If that won't work, look for a replacement circuit board.

Why do you suppose the b/u lights are on all the time? Both sides? just one? Trace the circuit board lanes the feed that lamp, see which mini-claw in the white connector feeds it. Is it in the right slot?

Yah, as I said, those things can me one crazy. High levels of the Volvo DIY hormone will support your persistence.

Good Luck,

Bob

:>)