So, this is kind of cool. For me, anyway, because I don't know much about electrical stuff besides basic wiring. As I mentioned earlier, I have an auxiliary gas tank out back (with its own fuel gauge), which was the truck's sole tank until I recently restored the stock tank and underlying sheet metal. So now I have two tanks, and two gauges. I didn't like the aftermarket gauge that went with the aux. tank. I wanted the stock fuel gauge to read both tank levels at the flip of a switch. After all, I have to manually flip a switch to select which tank feeds the engine.
Problem is, the sender for the aux. tank is different from the stock tank's sender, and doesn't calibrate with the stock fuel gauge. I tried, and even a quarter tank in the aux tank read out as beyond full on the stock gauge when I test-wired it. After some independent study, I learned that a fuel gauge is nothing more than a Ohm-meter for the resistance of the fuel sender in the tank. So I needed a way to adjust or calibrate the ohms from the aux tank to match the readings on the stock gauge. If I were meticulous enough to take careful multimeter measurements of the aux tank's sender between empty and full, then I could wire in the correct value resistors to compensate for the stock gauge. Instead, I took the lazy man's approach and installed a potentiometer so I could manually dial in the correct resistance to get readings on the stock gauge that semi-accurately reflect the fuel level in the auxiliary tank. Whew! That's a mouthful of electrical jargon. I tucked it in behind the dash out of view, but still accessible for further fine-tuning if needed.
Anyway, here are pictures of the highlights. So when I flip from stock to aux. tank, I just flip the toggle on the dash to get it's level on the stock gauge. So the ugly aftermarket and poorly mounted aux tank gauge is gone. Now I need to figure out what to do with its gaping hole. I might just install a block-off plate that will eventually serve as a CB mic mount.
