Does anyone know what the rocker switch under the ash tray activates? What is the blue light bulb above the speedometer?

 

Rocker switch may be for main/aux tanks. Do you have two gas caps?

Blue light I believe is high beam indicator.

Welcome to DF!

 

Welcome to DF! Do you have an owners manual? That may help you understand your vehicle better.

 

sounds aftermarket like something a previous owner installed.

These trucks didn't come with aux tanks. not even as an option. They had an option for a larger tank which my truck has, but no aux tank option.

maybe post a picture of the switch and light you are talking about?

unless that blue light is the high beam indicator, then I doubt it is stock either.

you may want to trace the wires to the switch to find out what it does.