Love you!
Yep, my sled in the car is only wired I can best describe as 'half heartedly', so i'm pretty sure it only has one wire to positive and one to ground so that looks like the cure.
Nice one!

This will probably help my problem with my other empeg, which restarts whenever I restart the engine and cuts out when I turn the lights on full beam (I must have driven 10k miles with my lights on low to stop my empeg cutting out!) ;-)