I have a Prestone Power Converter in my car and its acting strange. I cut of the cigarette lighter end so I could wire it to the battery. Anyway, it doesnt always turn on, when I hit the switch it beeps (it usually beeps if there is something wrong like reversed polarity). BUT if the car is off it works perfect, once I start it, I see the LED flicker and the unit dies out unit. Anyone experience this before?