[e015475]

The solution that DWCSR shows a link to is the only one I know that will work well without modifying the tank or sender

Whether you use a fixed resistor or variable resister, it matters not - the gauge will only be correct when the tank is full or empty and very unlinear between the two. A pot will allow you to fine tune it a bit at full, but not much else

If you use the resistor - fixed or pot, here's how your gauge will read-

Tank is empty, gauge reads empty (so far so good)

Tank is a quarter full, gauge reads half full

Tank is half full, gauge reads three-quarters full

Tank is three quarters full. gauge reads 90% full

Tank is full, gauge reads full (back on track!)

There are several other options - all fall into the category of 'science projects'.

-There are several micro-processor based solutions on the net, including some with Arduinos. (this has the potential to keep me sidetracked for at least a couple months)
-A simple transistor arrangement can be used to vary the current to the gauge proportional to the input from the tank sender.

I'm not savvy enough for either of these two solutions, and I want my gauge to be accurate, so I'm going to modify my tank to add another 0-30 ohm universal sender and abandon the 0-90 ohm. A universal tank sender is about $35 from Summit. I'll have to cut another hole in my tank but I've not put any gas in it yet, so at least I don't have to dry it out.

The universal 30 ohm sender seems to be the best solution with the least amount of clap-trap and dollars.