Not a Surf, but a bit stuck

[MudSurfer]

Greetings clever peeps. We have an old Massey Ferguson 590 and I put a new fuel gauge on today. Nothing at all happens, but when I connected the ground wire from the light, the needle goes all the way to full. I checked the old gauge, and it did the same.

Why would that happen? It did it with the lights off as well as on.

[RebelV8]

Connecting the ground wire shorts out the gauge, proving that the gauge itself is working. Check the sender, it's probably where your problem is

[markp2]

Hi,
Sender or wiring issue. It has been a long time since I have worked on a 590 but I think the sender can be accessed through a hatch in the cab floor. Corrosion on the connectors going into the tank sender is a likely cause.
Mark

[MudSurfer]

Cheers guys. It's a bit of a labour of love this old thing, spent £3k getting some of it up to a reasonable level and have done loads since, new injectors, new starter after rebuilding the old one twice, now it's time to get all the dials and gauges working.