I notice with my '99 Lincoln Navigator that after shutting of the engine, the radio will continue to play, even when the key is removed, then turning off, as it should do, when the door is opened to exit. Now, I understand why it would go off after opening the door--that only makes sense. And I thought the idea of being able to continue to listen to music on the stereo with the engine off was a good one, too. But, while waiting for a bay to open at the local JiffyLube for my overdue oil change and listening to the radio, it simply shut off after around four or five minutes. I could "reactivate" the radio by turning the key to "on" and back again (without starting the engine) and I could listen for another few minutes, and the radio would go off again. This has happened before under the same circumstances.
When I talked to a tech at a Ford dealership around here, he said that there is no accessory mode, like all cars used to have, in the navigator. He went on to say that Ford probably has some sort of smart chip in the system someplace that notes the power drain and shuts the radio down after a few minutes to preserve battery power. He guessed that the sound system in the navigator, which I got to admit is pretty kickin', might draw enough watts that to run it for very long with the engine off might result in problems starting.
I was wondering if anyone out there has experienced this in their navigator or, I would imagine, the expedition as well. If it does draw that much power, I guess there isn't much I can do, nor should I. If it doesn't, might there be a work-around whereby one could continue to listen to the sound system without it shutting down quickly? Interesting problem, though.