Since the problem is commonly caused by having the bulb holders reversed, and that is an easy fix, let me restate what's needed: Black on the driver's side, white on the passenger side.

If that is now correct, check the white bulb holder to be sure that the bulb is inserted correctly, not forced in "backwards". The pins on the bulb base are at different distances from the glass, and the slots in the socket are of different depths. The pin nearest the glass goes into the slot with the least depth.

Another possibility is that the slots into which the bulb holder fits may be compromised such that the wider "key" on the holder can fit in wrongly. There should be only one wide slot; the holder must fit in such that the ground tab touches the copper film that is on the the outside of the circuit board corner.

Determine the ground tab by inspecting the bulb holder. The tab which is in contact with the base is ground. The other tabs are the hot side of each of the two filaments.

These are quick fixes, so if the problem remains unsolved, post back and we'll keep trying.

Good Luck,

Bob

:>)