2002 Volvo S60 turn signal

You could have a bad bulb. The quickest way to check and compare the bulbs would be to turn on the flasher. Look at the rear lights. Do both left and right flash and are bright? Do the same with the front bulbs. I suspect that the right front will be dimmer then the left. If that is the case just buy the bulb from Volvo. I believe it comes with a new socket as well. If both bulbs are bright while checking then check the side marker signals also on the fender. If the right side is not flashing then that is the problem. If all of the bulbs are good then the turn signal switch itself could be failing now.