on my 2000 obw the left side foglight and head light sometimes dont work and other time they do. could it be a fuse, bulb or a relay issue? and when you change one bulb should you can them both?

Electrical socket and grounds i would check.

 

nipper

on my 2000 obw the left side foglight and head light sometimes dont work and other time they do.

The fog light only works with the low beam.

The relay that controls the left side may be failing.

(There are two relays - one drivers side, one for the pass. side)

I will search for a wiring diagram showing how the fogs

are triggered by the low beams.

 

when you change one bulb should you can them both?

Always a good practice, keep the working lamp

as a back up.

I had the same issue this week on my Legacy - the plastic tube that sorta shields the wires to the fog lamp, had filled up with muddy water and corroded the contacts inside the connector plug. A quick buzz with some fine grit sandpaper fixed her right up (and i cut away an inch of the shield to stop it happening again).

 

Try checking the contacts at the fog lamp end and see if theyre all green 'n gunked.

I had a similar problem on my '00obw but since yours is impacting the headlamp and fog light maybe it is different. My problem was with the bulb I think it's the H1 style in the headlamp that has that spring wire contraption to hold the bulb in place. If I even touched the spring wire then the bulb would work again. I had to bend it some, sand it, etc to get it working again. It didn't appear to be corroded or anything.