I put in an aftermarket ambient temp gauge (some japanese brand) a while ago, and i wired the light to the rear fog lamp fuse. (only one open) as a result, the gauge light goes off when the high beams come on. i want to tie it in to the same circuit as the small clock, so it dims with everything else. which of the three wires on the clock-tach harness powers the light? (i would guess the black is ground, so that narrows it down)

thanks for the help
mike