Homemade gauge test tool, C-3826

67Dart273 said
The procedure is in all the factory shop manuals. All it does is substitute known resistance for the sender. So, say, if you think you have problems with the fuel gauge, you first make sure it has "solid" 12-14V to the instrument regulator, and that the regulator is probably OK.

Then you unhook the sender, and clip this from the sender wire to ground. There are 3 switch positions which give you the "empty", the "1/2" and the "full" mark on the gauge.

If that does not happen, you check the sender wire, and move the box up to the gauge cluster and retest, or check resistance and connections on the sender wire.

If that's OK, you are getting up to either a bad gauge limiter or the gauge itself.

What I've read indicates that all these vintage cars used the same gauge movements, so this box should work with fuel, temp, or optional oil gauges.

I plan, later, to build a 5V regulator into the box so I can also substitute the voltage limiter

Thanks. It seems so simple. I have wondered in recent years about making some sort of device that would give accurate gallon readings on the gauge. When I worked at the Grumman Low Speed Wind Tunnel, we had to calibrate the balance by taking readings (data points) of measured loads on to discern the historesis in the structure. The forces at the data points became the new "zeros" in the system. Of course, we had analog strain gauges, which fed into an A/D converter, and then into the data acquisition computer.

Is it possible to use such as system to accurize a gas gauge? The system could be calibrated by loading one gallon at a time and taking a data point, which would correspond to "one gallon" on the gauge. Of course, this would require some sort of computer chip that could take the non-linear ohm output of the sending unit and convert it to a linear input for the gauge. I wish I had something like this during the "gas crises" in the early and late 1970s because I would have had a more accurate read on my potential range on the interstate highways when too many gas stations closed early. I should dust off my old electronics lab and text books.

Is this feasible?