Is there any possible way to make a little circuit to adapt a fuel gauge to a sending unit with the wrong ohm range? Specifically, I want to use a particular fuel guage that expects a 30-240 ohm range, and my existing sending unit is 10-73. This is a factor of 3 across the range (close enough), so I'm really wondering if I can somehow make it work. I expect that classic car folks must run into this all the time when they want to switch to modern gauges.
If you could get inside the gauge cluster and see if there is a series resistor in line with the meter movement, you might be able to change the resistor value to get a wider range.
Other wise, a electronic impedance convertor would have to be built.
All the aftermarket outfits sell universal sender units for the gages they sell. Most have adjustable arms and adjustable depth as well. I just changed out a couple in our fire engines because I got really fed up not being able to tell how much fuel was in them.
As for adapting the gauge itself. That can be interesting. What I have done on custom installs is to use a gauge movement from the company that made the sender. Then attach it behind the original face and use the needle from the factory gauge. Looks original and works well.
I have another one to do as soon as the latest rig gets out of the shop. It started life as a F800 with a frame mounted tank, it now has twin tanks and no real working gauge for fuel level. The plan is to replace the factory gauge with a unit from Stewart Warner to math the senders in the tanks. Then a simple toggle switch to select the proper tank. The fuel flow is already selected with a mechanical valve. Maybe I can make a cam to slide over the shaft on that valve to select the proper sender??? Hmm, have to look at that one.
Looks to me like I could put a resistor in parallel with the gauge and get it to work possibly. The resistor value would be about one half that of the gauge internal resistance. I'd need to really do it to be totally convinced though. The downside is additional current going through the sender, and I have no idea how much they can tolerate (before they get hot and cause my entire car to explode).
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