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You are absolutely right. Furthermore, I resent being lied to by a gauge.
Some time ago, and I didn't date my notes, I started comparing the half-dozen or so TC boards I'd accumulated, coming to the conclusion they were all functionally alike, just assembled slightly differently to improve the board layout.
Then I used a protractor to find the gauge face is actually an arc from 8:00 at the bottom extreme to 10:00 at the top of the red - just so we can agree on what 9:00, 8:30, etc. really indicates.
Following that, I used a variable resistor to map the sensor resistance to gauge positions with and without the TC board in the circuit-- and effort to see just how "big" the lie is.
The TC board uses a voltage comparator with two setpoints to determine a range for which the gain of the circuit is modified. The result is a reduction in meter deflection for the middle range temperatures only. That still is supposed to let it fly to the top when it crosses the upper comparator boundary, and bring it off the bottom quickly while it is first warming up.
All in all I just convinced myself I didn't want the thing in my car.
--
Art Benstein near Baltimore
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