Have just bought a 1985 LR90 (see Introduce Yourself thread). The fuel gauge has been playing up since I acquired the thing - initially not registering then going to full deflection with the tank 3/4 full. I've done some testing with the gauge in the car and also on the bench. The initial results seemed to indicate the sender so I bought and installed a new Britpart, with the result that the gauge simply went to full deflection again. I've removed the new sender and the gauge from the car and wired them up on the bench, driving the gauge from a 12v DC power supply - same result but noting that the gauge moved slowly with the float at 'empty' and much more quickly with the float at 'full'. The sender variable resistance coil is giving a linear 8 - 200 ohms approx when measured across the signal terminal and the float moved from full to empty. The Low Fuel Level warning light operated normally with the new sender in the car.
Given that the problem is replicated on the bench this seems to be suggesting that its the gauge as well as the sender which was faulty - or am I missing something basic. The gauge and sender wiring in the car all checks out for continuity.
Any help with the diagnosis would be much appreciated.
Best,

Rob.

I hope you find an answer to this cos mine is exactly the same but again the low fuel light works so I just ignore the gauge

sounds like its wired wrong or senders faulty

It varies between year of build & exact model specs ...
White/Slate [grey] tracer to low fuel light
Black ---- earth
Plain green ----- gauge power 12v feed

On the sender - the centre stud is earth, the other two just connect, (if the low level light comes on & gauge reads incorrectly just swap the two outer wires over)...

330 to 13 Ω (complete range of the sender)

280 Ω when on the empty line and 14 Ω completely full on most gauges

Reading high indicates a short...

Marmaduke said:

I hope you find an answer to this cos mine is exactly the same but again the low fuel light works so I just ignore the gauge

Click to expand...

Thanks James and Dippy.
By substitution the problem seems to be the gauge. Tried a borrowed gauge which responded in the correct sense to movement of the float when all set up on the bench. So new sender is working correctly and 200 - 8 ohm resistance was limited by the setting on the multimeter. I suspect it would go to 300+ ish. From previous testing I think the wiring in the car (which matches Dippy's colour ways) is OK so hoping that a new gauge will resolve the problem. BTW Marmaduke the low level light worked OK in mine too - the sender has a separate switch for it. If a new gauge doesn't work............................
Best,
Rob.