I'm going to test its current draw. What should I consider excessive (i.e., I shouldn't 't leave it on permanent +12v if it draws X amps)?

Never mind, can't test its current draw. My little multi-tester thingamajig doesn't seem to have that capability, there's no "amps" setting on it, only ohms and volts.

Interestingly, when I pulled the power from the GPS, it stopped sending data to the player on the serial port. I thought it would keep going as long as there was a little charge in its battery. So I'm thinking maybe the battery in this thing is shot (it did sit on the shelf for a long time before being sold).

So I'm going to wire this thing to permanent 12v in the car. Anyone think this will result in a dead car battery? Anyone have any idea what this unit draws, and how long I'd have to leave it in the car to make it drain the car battery?