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Fuel tank sender units


Andy

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According the bits of paper I got with my S3 it's got a S1/2 fuel tank. Now assuming it came with a S1/2 sender unit is there any reason it wouldn't work with a S3 gauge?

Currently the way it seems to work is full = empty & 2/3rds full = full. I'm wondering if a positive earth truck's sender unit would make the gauge work backwards & a different resistance range could explain the lack of movement in the gauge?

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The various ages of gauges and senders vary in their compatibility. You do need the correct sender. Sometimes you will get a zero reading when full, then a full reading when the level lowers just a little - this just needs a bit of bending of the float arm to stop the rheostat going past the end of the contact area when the float is highest.

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Sorry I didn't explain it that well.

When the tank is full the gauge shows 2/3rds full BUT when the tank is empty the gauge shows full. So it's travelling in the wrong direction to just bend the arm to sort it.

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Still possibly will sort it, though it is a different description to what I thought I had worked out before ;)

It may be that the sender is falling off the bottom of the rheostat and shorting, giving a full reading. It is certainly the cheapest option to try and bend it for sure.

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Well I've kept the tank nearly empty so I can poke my hand in & fiddle with it. Then I can see what the gauge says. Guess if that doesn't work & the sender gives a smooth change on a multimeter then I'll have to get a new sender to suit.

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Well I've kept the tank nearly empty so I can poke my hand in & fiddle with it. Then I can see what the gauge says. Guess if that doesn't work & the sender gives a smooth change on a multimeter then I'll have to get a new sender to suit.

That could be a problem. Early senders are screwed into the tank, later ones (SIII) are a sort of twist-lock idea. They don't interchange. Guess how I know..... SIII tank and sender in a Series IIa... Empty reading with a full tank and a very very floppy needle... Reads full when half empty....

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That could be a problem. Early senders are screwed into the tank, later ones (SIII) are a sort of twist-lock idea. They don't interchange. Guess how I know..... SIII tank and sender in a Series IIa... Empty reading with a full tank and a very very floppy needle... Reads full when half empty....

Now that sounds possible as I've got a receipt that came with the truck for a S1/11 tank. Might be time to say bugger loudly then. Still the tank is virtually new looking so I guess I wouldn't loose too much swopping to the right one to get a compatible sender.

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In about 1967 Land Rover revolutionised their electric system by installing a black instrument panel with flick switches for the lights and wipers and a key switch for the ignition and starter. Among the more revolutionary innovations was the installation of a temperature gauge rather than an ammeter and a change to the slow-reading type of fuel gauge.

Both temperature and fuel gauge in fact operate at about 10 volts and are controlled by a voltage regulator which is a small rectangular box bolted to the back of one of the instruments (On S3 its the speedo!). The tank units have a different resistance and the corrrect one must be used to get the accurate reading.

All SWB gauges are fixed by 6 screws - and the tank mounts are the same for both types - so they are interchangeable. The later units have a flat top, the earlier ones are raised. Later ones are freely available - earlier ones may be unobtainable.

Diesels have a terminal for the low level warning light. A diesel sender can be used on a petrol - simply leave the terminal unconnected. The terminals are marked with letters - T is the gauge and W is the light.

Later LWB's have the tank under the floor at the back - and have a bayonet fitting sender unit - as well as a different (shorter) float arm as the tank is shallower.

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