Much discussion on the sender but no reminder that the in-dash gauge depends on a built-in +5V Voltage supply/reducer that is basically a rather crude device and certainly over 50 years old. This +5V signal also powers the temperature gauge so if the temperature gauge seems to be working credibly the Voltage supply is probably working OK, also.
Having a good ground from the steel base of the sender to the frame is critical and may be enhanced with a wire from an added lug on the base to a convenient spot on the frame. And, of course, the engine to firewall ground connection needs to be corrosion-free and snug.
I don’t think there is anything in the sending unit other than resistance wire wrapped around a tube with a slider finger attached to the float riding back and forth across the wired tube. In some cases the tube itself may be curved to improve linearity. Between “F” and “E”, one is at the mercy of the tank configuration and float-resistor geometry. I believe I have noted some gauge lettering and indicator points appearing to be non-linear, suggesting that some attempt was made to correlate needle position to actual gasoline left.
Even before I became an engineer, I always wondered why modern technology could not tell me ‘zackly how much gasoline remained in the tank. I always thought there might be some sophisticated and calibrated system that took into account tank configuration, grade angle and other considerations. What a let-down.
I appreciate, but don’t totally trust, the digital technology on our ’05 Durango—especially DTE—Distance to Empty. All manufactures will fudge a little on the low side to avoid being sued by drivers depending on the data presented. But, I also realize that the purely mechanical and reasonably accurate trip odometer on every classic Chrysler 300 should override any gauge indication. Use it and try to remember to reset it.
Then you have the variance of philosophy and risk tolerance between pilot and copilot. Pilot is comfortable with rolling into a refueling stop on fumes as being an efficient use of precious time. Copilot starts reading over pilot’s shoulder at the gauge and starts freaking about ½ full indication as some of our cars’ gas gauges dropped slowly to ½ then dropped like a rock in a well below ½. “Trust me” statements have no effect. This is especially true when travelling the 259 miles from Ely to Fallon on Highway 50 in Nevada. Depending on what one is driving, it may make sense to top off at Eureka and/or Austin.
Finally, who needs the “u” in the word gauge? In Nebraska, anyway, “Gage” works for a county name and sounds the same. Maybe the “u” is for “you” to use your noodle to keep from running out of gasoline.
Brentwood, CA (Near 90 today)
That is great info Dan; if you have it , by any chance, Bob has been putting stuff like that up on the site…that would help a lot to have a way to know arm is about right ; mine goes beyond F when full, thinking about bending float up, would help ( then sender arm is down some at real F, but ----would head to E even faster..!!!! “””So bending it down is probably right so it reads something like correct at ¼. After straining head about it , I left it alone. Too much work to take out again.
Posted by: "Rich Barber" <c300@xxxxxxx>
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