Gas gauge calibration unit

A micro-controller seems like overkill, but I know some are so cheap they cost less than a precision resistor. However, that only works for high-volume automated assembly, not people handling soldering irons. I bought 2 electronic IVR's for <$30 ea w/ shipping. Search "voltage limiter" on ebay.

I agree with others that what we really care about is "where exactly is empty". I can remember that I filled up for at least a few days, so no big deal whether the needle is exactly at "F". It is weeks later when I need to know "how much left?".

To adjust zero, you can add series resistance if it reads too full, or add parallel resistance if it reads "E" too soon. Both are fairly easy and could be done at the kick panel body connector. To also adjust the full reading, we need "another knob". One way is to booger with the IVR output voltage. I haven't looked close at my electronic ones, but might be possible by adding series resistance or changing the "sensed voltage" feedback.

However, above is beyond most people or not worth their time, so I can see where a store-bought box would sell well if the price is right. It would be fairly easy for a user to install such a box in the kick panel (though might need 12 V power there). The same basic box might work for many classic cars, but would need different connectors. At least that could get the PCB volume high enough to reduce unit cost. I am surprised those clever Chinese haven't done so already. If they can put a computerized voice in a greeting card for $2, they could build an affordable "fuel gage fudger" box.