Fuel gauge jumps straight to max

[Spanners]

Recently acquired a Morris 61 deluxe. It was positive earth now converted to negative, everything fine for 4 days and today the fuel gauge now jumps straight to max, sender wires are fine. If I disconnect the centre one still stays at max. When I disconnect the black/green wire at the gauge stays at max.

Voltage ign on at green/black wire at gauge is 7.5.

Am I right in thinking pre '64 has no voltage reg so therefore it's the gauge at fault?

Can it be tested on the bench?

[Spanners]

This has happened before but I've had a notification that gogsymac has replied but there is nothing showing at my end when I check the post, does it have to be approved first or something?

[gogsymac]

No - sorry. I misread your post and added an answer which was incorrect so I deleted the post. Apologies for any confusion.

[Spanners]

That’s ok, no apology necessary!

[Spider]

With the pre-regulator type gauges, the senders work back to front to the later type.

When full, the sender is at maximum resistance and when empty at their least.

Removing the sender wire will make the gauge show full. Briefly short it to Earth and it should show Empty if the wiring and gauge are OK.

I'd guess it's the sender.

[Polarsilver]

I had similar issues other than on a Moke & it was the Sender.

[Spanners]

Ok so disconnected it shows full, looks like it is the sender then. Fab thank you, will test it tomorrow!
Only had the car for a month so lots to discover about the early models.

[Spanners]

Broken wire in the sender, quick solder and all working again. Looks like the original still so it's done well.
Many thanks for the advice.

Will.

[Spider]

Nice find and fix !