Fuel tank sensor and gauge

Davey · 2015-12-07T12:14:29+00:00

I have to debug an old-style fuel gauge problem this winter, it never moves. I will first check that the gauge is wired correctly, and has power. As I see it, the gauge is really an ammeter, the current depending on the resistance of the potentiometer in the sender unit. Before tackling the tank sender unit, what sort of current should I be able to measure passing through the gauge? If it is about right, then the gauge would be indicated to be faulty. But if the current flow is high or none, then any of the gauge, the sender, or the wiring, could be at fault. But knowing what sort of current should flow would be a help to start with. Any suggestions welcome.

Dec 07, 2015 21 Replies

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Davey 10 years ago

I know what you meant. But the Lucas BM uses the current flowing through the wire, or coil, if it's coiled, acting on a magnetised vane to move the needle. This is not a voltage drop across a shunt, it produces movement of the needle depending on the magnetic force generated by the current. An Ammeter by any reckoning.

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Dave Plowman (News) 10 years ago

Yes - forgotten about those. Lucas trying to find the very cheapest way of doing things. ;-)

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