There may be a simple answer but after a long day, my brain is fried. i need input on a PCB friendly component best suited for switching between ground circuits.

input/operating voltage:
Primary circuit - 11-14.4v
Secondary circuit input - 11-14.4v

Primary circuit powers the LED at full brightness

Secondary circuit changes the ground path to apply an additional resistence. the intent is to reduce brightness by 50-75% during low/no-light conditions. The resistor value for the secondary circuit will be determined before final installation. this requires end user (in person) to provide "brightness" input.

In short, i need a component to switch ground paths when the secondary input voltage is applied to it. A mechanical switch is not feisable solution for this part of the circuit (PCB).

I will be using a magnetic switch to apply the chassis ground to the overall circuit. The total assembly will be covered with a plate and this was the easist way to keep the circuit inactive while the cover was in place.

I value your input. Thanks

 

This really isn't clear. If you want two brightnesses, just have one power source turn on a transistor that shorts out one of the resistors. No need to mess with ground.

 

It might be easier to do it all on the high side. Can you do it like this?

 

I appreciate the input. I am aware of a couple of ways I can control the high/power side. I know it looks unconventional but I am still after controlling the ground side only. I do not want to use a standard automotive SPDT switch or relay.

 

I think an MAX4660 will do the trick.