[O'Man]

My 72 fuel gauge (factory original sender and tank) pins the needle past full when the key is turned to run. Turn the key to "Off" and the gauge backs off to just below full. This occurs with the tank full BUT even with the tank down 5 gallons the same think happens. Only difference between the tank 100% full and the tank down 5 gallons is the amount of distance past / near "Full" that the needle reaches. It goes further past full with the tank full than it does with the tank down 5 gallons. I put an ohm metter across the leads from the sender and it reads 151 OHMs with the tank full....approximately the same reading with the tank down 5 gallons.

I am thinking the sender is hosed but not wanting to jump in and tear it apart I would like to get some opinions. My research says that the sender should test out at between 0 Ohms (empty tank) and 90 OHMs (full tank). This might or might not be the right number because there is some variability in what my research shows. That said nothing I have dug up says 150 Ohms for a full tank.

Whats the smart money say on this...sender or the instrument head? Any theories on the 151 Ohm number is appreciated.

Thx

 

[Capt Casey]

I'd agree with you it's the sending unit...unless you checked the actual gauge in the dash for continuity resistance. They seldom break down unless you had the dash out recently? Wired in a new component to the same circuit? If so that could be the issue. But I remember mine going like that. It was fuller than full then after a few gallons gone it dropped like a rock to less than half.

 

[billdini]

Here is a previous post that answers your questions. If your meter is accurate your sender is deflective or the ground for the sender has a bad connection.

Testing Fuel Sending Unit

Can I test the sending unit with it out of my gas tank? I tried grounding it and both setting it in water as well as moving the float manually with a "0" reading at all time. Any input?

www.chevelles.com