The n/s main beam on my 2005 S60 D5 was out when I took it for its annual inspection (fortunately they passed it anyway!). I interchanged the bulbs and both worked fine. I checked the earth on both sides via the bulb connector, both were fine, there was no power at the live side of the defective side when the column switch was activated. I checked fuses 22& 23 (10 amp) and both were fine. I assume there is a double pole relay (one side for each lamp) controlling both headlamps and that one side has failed. Has anyone had a similar problem, I'm not sure where the relay is but assume (pray) it's fairly accessible and a standard 'off the shelf' item. Any suggestions?