Hi gaolow,
I did not really take note as someone at Car Beauty installed for me at $8. I was told that I can switch off the DVR using this switch instead of pulling out the power plug. However, I am not sure if the switch also power off the power saver, which I am trying to clarify with Xavier now.
As of now, I think the only sure way to reduce battery drain is to unplug the whole car battery, which of course will also disable your car alarm
think most likely they install between the camera and the power saver..to turn off the power saver, you need to install the switch between the power saver and the battery which is the yellow cable on the power saver.
you can do a check on the switch on what the color of the wire did it connect to or trace the switch wire to see where it lead to.
the power plug to the camera is a solid black cable with two wire in it if you cut off. this cable will have a ciga type of plug at the end where it plug to the power saver. on the power saver, there is a red LED to indicate there is a power feeding to it. if you turn the switch off and the LED still solid light on (not blinking)on the power saver, then it confirm that the switch is connected between the camera and the power saver..in this case, it dose help to prevent battery drain as power saver still suck current from the battery.
but, another possible on why your battery dies early is either a faulty power saver which did not cut off the voltage from the battery or you set the cut off voltage too low, like 11.8 v or the time delay too long..like 24 or 48hrs