V11, you're right, I think I connected the neg lead first, in error. Still, I'm surprised there's a current draw in the power line, even when the GPS is unconnected.
Kiwi, I would have connected the GPS directly to the 12v current too, but fortunately I checked some online forums first, and had previously disassembled a cigarette plug and seen the circuitry inside. Or I would have made that mistake too.
It's all powered off a small after-market fuse panel, that's nice because it fits so well in the tight space that cycles have.
Joe