I recently acquired a police model dome light ( Red and white light) with only two wires; a positive and a ground.. my truck has one positive wire and is self ground for the dome light. How would I wire the dome light to function as the original ?

 

What year ranger?


Not sure what you mean?
You would ground the new light to the cab, same as current dome light is grounded now, self grounded using the same screw

Then use the current dome lights positive wire for the new light

If you want it to change between white and red you have to use the switch