Odd fuel guage problem

[Brian28]

My fuel guage wasn't working a few weeks ago, was a break in the wire somewhere so I spliced in another bit of wire and all seemed fine, registered 3/4 full. Was driving it last week (haven't used this car much) and the petrol light came on, so stuck £20 in, that moved the needle about 1/4 tank from under 3/4 to over 3/4. I thought the sender float may be stuck or something so was taking it out earlier on and there is something odd going on. With the sender wires disconnected, the guage reads 3/4 full with the ignition on, rising about 1/4 tank when the wires are reconnected. I've tried different clocks, the starting point with the wires disconnected ignition on anywhere between 1/4 and 3/4 full. The wire I spliced in was much heavier than the original wiring, would less/more resistance in the wire make any difference? Or anybody got any ideas? I'm suspecting that the original wiring may have a short onto earth somewhere, but can't imaging that a bit of contact through wire chafing or whatever would stay absolutely constant contact when driving.

Cheers
Brian

[Brianmoooore]

Very odd. Gauge of wire makes no difference.
Have you disconnected the original wire at both ends, or just connected the new one in parallel?

[Brian28]

Bit of an update after a lot of swapping and fiddling. Part of the original wiring was shorting to earth, thats why it registered with the ignition on and sender wires disconnected. I've cut that out, sender disconnected ignition on, no fuel guage reading as it should be. But, with the sender connected it reads half full when there isn't half a tank in there. I've left the sender connected and lofted it out from the tank to drop the float, the fuel light comes on but the guage still registers half full. I've swapped the sender with the one from the race car and it is still the same, have swapped the clocks again and still the same. Any ideas?

[Brian28]

Sorry Brian, had replied before reading your post. Yup, was in parallell but I've isolated the old wiring now, updated as above. Still scratching my head over this ...

[Brianmoooore]

What happens if you totally disconnect the wire(s)?

[Brianmoooore]

I've just replied without reading your previous post!!
Have a look under the round access cover under the rear seat. You may have the duel sender set up.