My low beams occasionally don't work, usually when I go to dim the lights from high. Is this likely the light control relay, or is there a different relay for this? How do I test the relay if the lights are working OK, or do I have to wait until they don't work (usually when I'm driving at night, oddly enough)?

94 850 153k
90 745T 135k

I had similar problem, worked sometimes or was very dim others. Finally fixed by splicing in an additional wire to the ground wire and grounding that wire directly to sheet metal on the therory that I had a bad ground somewhere. It has been good since.