Wema sender VDO water guage

[Portofino]

Been trying to get the water guage a VDO on the dash working .
The exsisting sender is a VDO. Two metal rods .
The guage Allways reads full when the ignition is on /engines running etc .
When unplugged @ the sender end moves to E ,same as when the dash is switched off -keys out etc .
There's 24 -26 V at the sender end of the wire .
I have removed the old sender and while connected dipping it in and out of the top of the tank ,no change ,@ the guage still reads F .
The new sender is a 4-180'ohms WEMA float type .
With this connected guage reads F ,or E when unplugged .Dipping it up and down in the water ie altering the float hieght makes no diff ,guage still reads F .
However if I disconnect the wema guage and measure the resistance by moving the float up and down ( connected to a multimeter ) the R changes 6-190 ohms as it should ,so I know the "new sender "works .

wema -Summary 24/26 V @ the sender , resistance alters 6-190 ohms --guage reads F all the
time -

So is it the guage which is a VDO ?
If so what should I replace it with --another VDO or a wema for compatibility reasons .std 52 mm Dia dash guages .
Or an I missing somthing ?

 

[Boat2016]

Is it one of the blue senders with 2 metal rods? If so its a capacitance sender and uses a different gauge to the resistance type (4-20ma)

 

[Portofino]

Yes it s a blue sealed unit two rods
Aarrh - I've bought a Resistance sensor .Boats nowts ever simple ,

 

[Portofino]

New " blue "fitted all works + calibrated
There's wema type on the holding tank so I'll just keep that as a spare