Very common problem on the 98s (suprised you have not seen it

before). Most often, it is the left one (it sits on longer at

left turn stops). I believe there is a recall in progress to

update the bulb sockets but I have not yet recieved a notice

for my 98.

Get out the manual and look at how you get at the bulb (taking off

the lens cover is easy once you see how it is done). Pull out

the bulb and I bet it has some slight burn marks. You can clean

the marks up with some sandpaper or just get another bulb. That

should keep you going until the newer sockets become available

(actually, I think they are going back to an older socket

design).

IPD also sells a bulb that has a ceramic base (instead of platsic)

that is supposed to resist the heat and associated burning problems.

www.ipdusa.com.

Oh, when the turn signal bulb fails the side marker light

seems to flash. So, that is probably what you are seeing.

Kinda uses side bulb as a backup (but I don't know if Volvo

did it that way on purpose).