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The cigarette lighter is a simplistic design, it feeds from a 12v B+, and is fused. Just like the outlets in your house, when you don't use an object plugged into the wall, there is still a draw. The same is true for your vehicle. Some cars have the ability to detect draws from exterior/interior lights, usb and cigarette lighter ports. It's best practice to ...


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I would unplug it overnight or switch it off (seems like you can). If you just away for a few hours it should be fine because these devices usually don't need to much power. There are exceptions like chargers though.


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Normally, if the L terminal is for the light, then it will be positive when the engine is running and the alternator charging. The other side of the charge warning light is also connected to battery positive so if the voltages are the same then the light will be out. If the alternator is not charging at all, or not enough, then the voltage from the battery ...


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