65 Suburban Fuel Tank Sending Unit?

[jimmillac]

Hey RoyL. Are you trying to figure out if you really have a 30 Ohm gas guage? If I recall correctly, these old guages actually use a bimetal strip and heater circuit to move the guage with the heater current being limited by the resistance of the sending unit. I think it would be pretty tough to get an accurate resistance measurement of the fuel guage with an ohmeter because the heater resistance is going to change as the element heats up. What you can do though, is go to radio shack, get 3 10 Ohm power resistors (part number 271-132). Wire the three resistors in series (end to end). For this little test, you can just twist the wire ends together. Then, connect one free end of the series resistor to the connector that usually hooks to your fuel sender. Connect the other free end to a good ground. Turn your key on. If your fuel guage is truly 30 ohms, it will read 1/2 full +/- a little bit. Does that help?

[RoyL]

Originally Posted by jimmillac

Hey RoyL. Are you trying to figure out if you really have a 30 Ohm gas guage? If I recall correctly, these old guages actually use a bimetal strip and heater circuit to move the guage with the heater current being limited by the resistance of the sending unit. I think it would be pretty tough to get an accurate resistance measurement of the fuel guage with an ohmeter because the heater resistance is going to change as the element heats up. What you can do though, is go to radio shack, get 3 10 Ohm power resistors (part number 271-132). Wire the three resistors in series (end to end). For this little test, you can just twist the wire ends together. Then, connect one free end of the series resistor to the connector that usually hooks to your fuel sender. Connect the other free end to a good ground. Turn your key on. If your fuel guage is truly 30 ohms, it will read 1/2 full +/- a little bit. Does that help?

With the sender out of the tank, i checked the resistance across the 2 terminals, while moving the float, but got no reading, no connectivity between the two. So cant confirm the sender, how to check the gauge out of the truck?
Thx,
Roy
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