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Old 10-27-2009, 12:43 PM   #9 (permalink)
McTimson
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Join Date: Sep 2008
Location: Nyack, NY
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BMW - '97 BMW 318ti
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The unit needs a constant power source in order to keep the current and tank values. The calibration data is saved when it shuts off, but the other values are reset. That's why you can't just wire it in to an accessory voltage source on the car, because those are only on with the ignition. It has to be hooked up directly to the battery (with a fuse, preferably), in order to function properly.

The power drain is very low - I left mine in a car for over a week last winter without unplugging it, and the car still started up just fine. If your car is going to be sitting for an extended amount of time, then it would be a good idea to unplug it, but if it's only for a few days, then it should be fine.
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