nobber

nobber

Well-Known Member
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.
 
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..
Click to expand...
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
Click to expand...

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.
Click to expand...
sounds if theres a short in sender unit,green to earth full tank reading,through sender reading depends on resistance through the windings
 
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.
Click to expand...
did you do anything with the seal?
 
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.
 
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.
 
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