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Sat Oct 04, 2025 6:46 am

I have a 1956 Oval, its fitted with a VDO fuel gauge.
The wires go to earth and also to a connection on the outside of the fuel filler neck.
Its obvious that there is some kind of fuel sender inside the tank, but I have no idea how it works.
I was considering removing from the tank to have a look at the workings.

The gauge does not read well at all, but it looks great on the dash.
Does anyone have any knowledge of these gauges and sender units and can help with more information.

Sat Oct 04, 2025 8:07 pm

I have the same gauge in my vert,
I recently took it out the sending unit to clean my tank.
The 6-59 date on the sender tells me it was added years later.
Hope the pics help

Sat Oct 04, 2025 8:16 pm

Here is another post about the VDO gas gauge.
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Sun Oct 05, 2025 5:14 am

Great help guy's and fab pictures.
Just need to work if its the gauge not reading due to connectivity issues, or if I need to delve deeper and remove the unit.
First thing is to fill with fuel and see if the float, float's :roll:

Sun Oct 05, 2025 7:56 am

There not a lot of information on this type of fuel gauge. After a lot of research I finally found a nos instruction. Hope this helps.

Sun Oct 05, 2025 9:21 am

Take the wire attached to the sender and ground it to metal, if your gauge goes to FULL then it's not totally dead at least.
At that point you have to investigate the sender status.

FWIW one of these senders WILL work with that gauge (6v or 12V doesn't matter to the sender)- I just can't remember which one.
And it CAN be mounted in the filler neck like the original with a little bit of messing around with the bracket.

https://a.co/d/4OAGDIS

https://a.co/d/b7HGS0i

Sun Oct 05, 2025 10:52 am

I presume that's the live wire to the sender that you ground, with the Ignition on ?
Sorry Im a it of a idiot with electrical stuff.

Sun Oct 05, 2025 10:59 am

dee0861 wrote: I presume that's the live wire to the sender that you ground, with the Ignition on ?
Sorry Im a it of an idiot with electrical stuff.

No, there is no V+ to the sender. The sender goes directly to ground- and the resistance is varied by the position of the float.
There’s no risk in grounding the sender, when it’s at Full it’s running that circuit nearly directly to ground with no resistance.

Sun Oct 05, 2025 12:00 pm

Bub, thanks, but you are talking in language I don't understand fully.
I I take the wire attached to the outside of the filler cap and ground it will the fuel gauge read full if its working.
Then I can look at the sender as the source of the problem.

I did say, electrical is not my bag, but willing to learn.

Sun Oct 05, 2025 12:31 pm

Sun Oct 05, 2025 12:58 pm

dee0861 wrote: Bub, thanks, but you are talking in language I don't understand fully.
I I take the wire attached to the outside of the filler cap and ground it will the fuel gauge read full if its working.
Then I can look at the sender as the source of the problem.

I did say, electrical is not my bag, but willing to learn.

If you have 2 wires going to your sending unit one of them will be a wire that goes from the sender to metal, and grounds the sending unit.
The other wire will go from the sending unit to the fuel gauge; you can leave this wire connected, but just take a small wire and ground it to chassis/metal.

Some sending units have only one wire, and they ground through the fixing screw/bolt to the fuel tank, which is itself grounded since it is bolted to the body. *If you only have one wire, jump a ground wire to this one. The is no live 'voltage' connected to the sending unit- at least there should NOT be, that would pretty wrong.

You can also test it by grounding the signal at the back of the gauge: On the back of your gauge you have usually 3 connections.
6V+, wire to the bulb from headlight switch, and the other wire goes to the sender. You *might* have one extra wire that grounds the gauge housing, but they typically ground through the housing nand dash.
DONT ground the 6V connection, but DO ground the other one that might be labeled 'G' ?, This is the wire that when grounded and makes the needle go to FULL.

One way these quit working is the sending unit may have lost a good ground connection: take a length of wire and attach it to the metal part of the sending unit where it's bolted to the filler neck, and ground the other end. If this makes your gauge work a little then grounding the sending unit may be all you need to do.

Mon Oct 06, 2025 10:21 am

Thank you everyone who contributed to this post.
Brilliant information.

Gauge is good, managed to lift the sender up and got a good reading.

Then took the sender out of the tank, date stamped 5/56.

The float is cork, and not floating in the fuel.
On removal the cork was covered in a layer of reddish paint, which came off very quickly when I wiped it clean of fuel.

Just need to find a good float replacement, probably a more modern plastic one.

Thank you all.

Mon Oct 06, 2025 11:26 am

dee0861 wrote:
Just need to find a good float replacement, probably a more modern plastic one.

Might let the float dry out fully over a few weeks. Then coat with a fuel proof plastic coating.

Mon Oct 06, 2025 3:02 pm

56Cabrio wrote: I have the same gauge in my vert,
I recently took it out the sending unit to clean my tank.
The 6-59 date on the sender tells me it was added years later.
Hope the pics help

What date is stamped on the gauge itself? Might of had the sender replaced at a later date.

Mon Oct 06, 2025 8:26 pm

AlteWagen wrote: 56Cabrio wrote: I have the same gauge in my vert,
I recently took it out the sending unit to clean my tank.
The 6-59 date on the sender tells me it was added years later.
Hope the pics help

What date is stamped on the gauge itself? Might of had the sender replaced at a later date.
Hard to read but i think the last number is a 9
The gauge also has a 31/1 like on the sending unit.
Im eventually going to weld up the hole and put my Dehne gas gauge there
as I don't like the placement on the dash and think the Dehne looks better between the speedo and speaker grill.

Thu Oct 09, 2025 9:11 am

This is the sender unit stamped 5/56, so fitted about 4 months after the car was registered, 11/02/1956.
Replaced the cork float, using two demijohn corks, roughly the same size as the original ones.
Coated the cork to make sure its protected from ethanol degradation.

Gauge is now working correctly.
Happy days.