I've got an old aftermarket " no name" electric water temperature gauge. I'm sure it's 12V. But I have No idea what sender to use with it. The gauge is a 90* sweep, low temp 100*--280*. How would you check the gauge, to get the right sender? I'm sure some type of universal sender would work...but which one ?
A variable resistor and a 12 v power supply should be all you need. (Or 6 v power if the gauge is 6v) Once you figure out what resistance the gauge expects at different meter readings, look up sender units to match. Or just buy all the misc sender units you can find at a swap meet, and mix-and-match until you are happy.
You don't mention the brand. It matters because all Ford gauges are 6-volt except for 1956. That was the only year for 12-volt. As mentioned, use an old volume control or buy a 500-ohm potentiometer from Radio Shack. Connect the gauge in series with the volume control and s l o w l y turn the wiper. When the gauge hits 'all the way hot' do not move the volume setting, but disconnect the wires and measure the resistance of the volume control with a meter. That will be your sending unit's top value (like 10-90 ohms).
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