The relay is located alongside the "underdash" fuse panel in the driver's side footwell - it is unlikely to be your problem - all that relay does is switch the headlights (both high & low beams) on or off - so if the relay were at fault, both beams would be affected.
Focus more on the combination switch itself - or the wiring.
I agree with Max, as one of the issues I found on my GV was the connectors were not coated with a corrosion proofing when they were originally assembled. They developed corrosion and made poor contact. A bit of cleaning and application of dielectric grease to keep the moisture out of the connectors solved the problem.