Them there fuel level senders?

I take it they are a kind of sweeping potentiometer thing on the earth side? My needle goes way up past full and stays there, low fuel lamp still works.

Yarp, could well be a short to earth on the cable, sender to gauge.

Could just need adjusting?

What Im thinking is, less resistance on the coil - low reading on the gauge, so no earth on the tank would have the same result, the tank may need earthed. I will have to have a look at the wiring diagram for it.

Or possibly not, 3 wires, G/B to gauge, W/S to low fuel warning lamp and B to earth, so it doesnt earth through the tank, its on a wire, still could be that though, I will try removing the earth, see what happens..

Right then,removed the black wire/earth from the sender, nothing happened, gauge still reading full, so looking at the diagram, Green live from fuse to gauge, Green/Black from gauge to sender unit, then black to earth, the Green/Black is essentially the earth via a potentiometer, so that wire from gauge to sender has gone to earth, or the gauge has gone pear shaped.

Oooh, didn't think , if I remove the green/black wire, gauge to sender, thus removing the earth from the gauge before the sender, the needle should drop if the wire is good? Right? Because if it were earthing it wouldn't drop , am I right?

nobber said:

Or possibly not, 3 wires, G/B to gauge, W/S to low fuel warning lamp and B to earth, so it doesnt earth through the tank, its on a wire, still could be that though, I will try removing the earth, see what happens..

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thats correct,touch g/b wire to earth gauge will read full

jamesmartin said:

thats correct,touch g/b wire to earth gauge will read full

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So, if its reading full connected, then empty with the GB wire disconnected, the fault lies in the sender unit, the potentiometer is showing no or not enough resistance when the sweep is at empty. Looks like I will have to whip it out and have a look at it.

nobber said:

So, if its reading full connected, then empty with the GB wire disconnected, the fault lies in the sender unit, the potentiometer is showing no or not enough resistance when the sweep is at empty. Looks like I will have to whip it out and have a look at it.

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sounds if theres a short in sender unit,green to earth full tank reading,through sender reading depends on resistance through the windings

jamesmartin said:

sounds if theres a short in sender unit,green to earth full tank reading,through sender reading depends on resistance through the windings

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It sounds like the windings are bridged, or the sweep arm has gone straight to earth.

nobber said:

It sounds like the windings are bridged, or the sweep arm has gone straight to earth.

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Bet you can do a bodge/repair on the windings to keep it going, but I guess a new one is cheap enough?

I have the same issue - watching to see what you do.

New one is 30 quid, its the all in one kind. I pulled it apart, sweep arm was a little bent, straightened everything up and tried again, still the same, adjusted it , no joy, the windings looked worn so ran my thumb over them a bit, it now works, kind of, its still not right, its jumpy and probably not accurate, need a new one basically.

nobber said:

New one is 30 quid, its the all in one kind. I pulled it apart, sweep arm was a little bent, straightened everything up and tried again, still the same, adjusted it , no joy, the windings looked worn so ran my thumb over them a bit, it now works, kind of, its still not right, its jumpy and probably not accurate, need a new one basically.

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did you do anything with the seal?

NiallRussell said:

did you do anything with the seal?

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The seal is fine, that wasn't causing any problems.

nobber said:

The seal is fine, that wasn't causing any problems.

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when you reattached the sender, did you have to replace the seal? I thought if you changed the sender you needed to.

No, it was fine, obviously if you take the sender out and the seal is damaged it would be a good idea to replace it, what kind of vehicle do you have? There are different types of sender, and seal.

nobber said:

No, it was fine, obviously if you take the sender out and the seal is damaged it would be a good idea to replace it, what kind of vehicle do you have? There are different types of sender, and seal.

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110, 1985 originally a v8

Mine is an 85, but its a Ninety, its difficult to say which is yours, there is a plastic one and a metal one, both seem to lock in with a locking ring.