The project: Convert the mercedes benz 300D sedan to run on WVO (waste vegetable oil)

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The 6-port Fuel Selector valve has a SPDT switch inside designed for swapping the fuel gauge between tanks. I had ulterior motives however, and wanted to use the switch to light up a two color LED. This is the schematic. Major props to Der Fuhrer for the assist.

The dash with the switches installed. The left switch is a DPDT that controls the 6-port fuel selector valve. The right switch is a lighted SPST that controlls the dump valve.






The Auxilliary Coolant pump is controlled by a relay and designed to come on only when the heat is on. This would not work for our purposes so it was re-wired.

First, the heater control panel was removed.

The black / red stripe + purple polka dot wire controls the auxilliary coolant pump. I chose to remove the wire plug from its connector and solder it to the 12V supply for the dash switches which gets its supply from the cigarette lighter. Other methods could also be employed.