Quote:
Originally Posted by Formulabruce
Played with a TU-5 last week with a stock 70 gauge set. Mine was close, but not perfect, so being old and anal, I tried for more LOL. I wanted to see what "actually" happened to accuracy with a added resistor in line. So I calculated what I needed and had a friend put it way back at firewall. I noticed it nailed the operating temp, which was 180 water with a 160 T-stat,( and im sure well over 200 in the cylinders for those with efficiency in mind).
SO we changed out a few and it changed the gauge reading. I then hooked it to the TU 5 in hot water ( pan of water with jumper wires) to the gauges in the car. ran the water to 200, and got 200 on the gauge, 210 seemed right on..tried 150, was very close...Now I wondered why all the hype on other forums about it being not accurate.
The temp gauge itself has a resistor to make it compatible with the senders used at the time. So I figure why would an additional one make it not accurate at any other temps> and why would they say its accurate for the TEMP you make it but not others?
This info is FALSE. That said..The difference was this, the reaction speed was slowed a bit, across the board. going up and down.
Technically mine should have been as close as Steve's, BUT old "wound" resistors on back of a gauge can loose their insulation and some of their resisting properties making gauges read higher. The right way may have been to bench test the whole thing and make the total "back of gauge" resistance match with the sender resistance for accuracy. May have to do that someday..
so Im running a 20 ohm resistor... hehe
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Congratulations on the success. I would recommend you use a precision resistor, they don't vary as much to ambient temperature. A standard carbon film or wire wound, will vary as much as 10% with 100 deg temperature swing. Just a suggestion, again great work.