Well I've found out what the problem is here. Special thanks to Randall
Young and Dan Masters for great suggestions. Hooking resistors to the gauge
proved that the gauge is fine. I had given the sender a quick test before
installing and seen it change the resistance, but finding the gauge working
forced me to look closer. I found that the problem is the terminal itself
that the wire going back to the gauge connects to. If I pushed and held it
in different directions I could get the gauge to function (pretty much read
anything I want actually). I figured that even in a luxury ride like the TR3
I couldn't live with it being that flaky.
It turns out that the problem involves the hex shaped foundation to the
screw terminal and how it (often doesn't) contact the little metal tab that
comes up to it and is attached by wire to the variable resistor. I'm going
to clean it (somehow) and try to force them back into better contact (I'll
add a little Kopper Shield while I'm at it). Hopefully this will provide for
a reliable connection. I'd hate to give up on this sender --- it's probably
in the best looking condition of anything I've found on the car!
Thanks again to all for their help!
Dave Moag
62 TR3B (one tiny bit closer)
77 Spitfire
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