Gas gauge not working? I think I fixed it.

Since the day I picked up my 71 Duster, I have put in many many hours trying to fix the gas gauge. I finally discovered that the gauge did not need to be fixed.


I started with replacing the original fuel sending unit. Parts of it were missing and more than likely dissolved in the muck at the bottom of the fuel tank. Then I replaced the mechanical voltage regulator with a 5 vdc electronic voltage regulator. Thinking I am smarter than I am, I decided that I could tweak the gauge by adding resistance in series of the sending unit, Didn't work. Then figured I could reduce the resistance by adding resistance in parallel to the sending unit. Still did not work.


The PCB voltage regulator died a unspectacular death, so I pulled the instrument cluster again. This time I took a couple hours playing with the resistance on the test bench. You would think I would know better.


Thinking, the resistance in the sending unit is where it should be, the gauge was working but not as I liked it. So if the resistance of the circuit is set to OEM specs. What is the one thing that I had not tried to adjust. Back to Ohms Law, VOLTAGE


I set a resistor to match the sending unit and attached my variable power supply and adjusted the voltage to the circuit. Eureka …..... I went and bought a 5 and 6 vdc regulators, $1.59 each.
As the temperature gauge was working just fine at 5 vdc it needed to stay there. As in the picture I cut the trace on the PCB so the two meters can use separate voltages. In the picture the PCB has been modified a few times prior to this.
I attached the 6vdc regulator to the gas gauge and the 5 vdc regulator to the temperature gauge.
Prior to this time the gas gauge would read either full or empty, nothing in between. NOW the gas gauge is showing I have ¼ tank of gas left (Which is about correct)


I think I done it. I will keep an eye on it to see what happens when I add gas 2 gallons at a time. :salut: