Just to throw more fuel (ha!) on the fire... I did buy a new sender from Centerline. Unfortunately for dummies like me, it didn’t come with installation instructions. I took a stab at how to attach the wire feeds, and I got wild swings in the gauge readings. Having read somewhere that there are gauge-specific senders for Jaeger and Viagra (😁) gauges, I automatically assumed that I had received the wrong sender. So, I fired off an email to CL. First, they told me that gauge-specific senders only apply to pre-1969 gauges. Then he went on to explain various wire configuration that I should try. I did so, but I still wasn’t getting good gauge readings. My bogus assumption? I assumed that the sender was grounded through the attachment screws. Uh uh — turns out that you have to use the spade at the top of the sender (or a ring connector from a mounting screw) to a good ground location anywhere nearby. I tried that, and voila — accurate gauge readings!Just curious... Why a discussion of a Jaguar sender? New Alfa senders are reasonably priced.
But to your question...
A sender that has a different “span” than is intended to be used with a certain gauge, you are not likely to get an accurate E, and F, and/or the response in between will not correctly indicate how much is in the tank.
It is possible to create correcting circuitry to match a sender to a mismatched gauge, but this brings us back to why not just buy the right sender?
But it is interesting that the “Empty” resistance value of 90 ohms occurs before the float arm bottoms out; I.e., the gauge will read E when there is still some indeterminate amount of fuel remaining in the tank... which I suppose is better than running out of gas before the gauge reads E. Or maybe the float does in fact bottom out before the arm reaches the end of its travel distance...? Be that as it may, the non-empty readings of the gauge do appear to be accurate.
We now return you to our regularly-scheduled programming...😁