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Fuel tank sender - how does it work?


Staff member
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I am turning my attention to the fuel tank on the Vauxhall. The original sender is dead and of course they are unobtanium. Turns out a 1275 era sender fits the holes and I can adapt the float. However, from my Vauxhall forum I think it and the Vauxhall one might work oppositely. IE reads full when empty and vice versa. Could someone explain please how a sender works and how I can measure it with my multi meter. (off the car)

thanks all!


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The fuel tank sender is just a variable reistor. It will have a specific resistance when the tank is full and the resistance will either go up or down as the fuel level drops. Whether it goes up or down depends on the car and gauge used.


Jedi Warrior
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If it reads the wrong way couldn't you just reverse the connections to the gauge?

George Zeck

Jedi Warrior
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I am in process (& have read solid reviews) on the Tanks Fuel Gauge Interface:

Similar to the Spiyda recommended here, but available in the USA vs. shipping from over the pond.


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The gauge and sender on my '67 Sprite work the same as the older Sprigets, higher resistance at full. Later senders were the opposite, higher resistance at empty and the gauges worked an entirely different way. I'm not sure when they changed over but could be by '69. You can check your gauge if you don't have the original sender. The gauge that matches the high resistance at full requires a ground. The other style gauge does not. Of course that ground may or may not be a separate wire. It could be chassis ground. Not sure this helps as much as I thought it would. You can probably find out from your forum which style you need.
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