Fuel Gauge Sending Units compared
Can you explain how that works? It sounds backwards to me. If the voltage across the circuit is the same, than the lower resistance would have a greater current flow. Wouldn't more current equal more heat?
Yep. A hot gauge doesn't measure 20 ohms or 13 ohms, which ever type is subject. Resistance within a thermal gauge changes as the wire temperature changes.
The 13 ohm design is a lot different mechanically. The bitmetal is different. Even the pointer weight is different. For what its worth... if you have the later 13 ohm fuel gauge in your inst' panel, you will find the oil and/or temp gauge was never changed. Still 20 ohm type. Why? Oil and temp gauges rarely if ever go to the hotter end of function. So never was a early failure issue with those. I will add this, The 13 ohm fuel gauge is not as sensitive or accurate as the 20 ohm fuel gauge.
These OEM thermal instruments are basic range indicators. There are no gallon marks on the screen. Even so, a heck of a lot more accurate than what aftermarket offers.
Yes the tank shape could be considered a factor but, the vehicles stance doesn't hold the tank exactly level. The contact in the sender is touching 2 or more laps of that resistor wire at any given position. So exactly 23 ohms didn't need to be precisely in the center of the OEM senders arm swing. So is it? In the case of the rally fuel gauge for example the 23 ohm calibration target/dot is not exactly aligned with the half tank hash mark. Shape and stance of the tank is compensated right there. That's all I'm going to share here.
I don't know how many times I have briefly considered posting pics of S&W data sheets I have but.... The guy that sold this material to me warned, This stuff at exactly legal to have (stolen). 100 year copywrites have not expired. That's all I needed to hear.
