First off, the blue wire runs from the gas gauge, to the sending unit in the gas tank. Since this is an after-market gauge you are putting in, I hope it's matched to the resistance of the sending unit, otherwise you will get a incorrect reading. I can't help you with the temp. gauge. That picture you posted is the ballast resistor. That has nothing to do with your gauges. If you had an original tach. in your car, a wire would have run from the "-" side of the coil, to the tach. A wire would have gone from the "+" side of the coil to this ballast resistor. I hope I didn't confuse you more.
Mike
