Help needed please...fuel gauge

[Mindi]

Have had a Vthree/Teleflex universal sender in the tank and a Faria 2" gauge together OK for years but I didnt install them. Last week noticed the gauge only moved up from rest to a bit below empty.... (the tank is 75% full) and stopped there. Then my brain went soft....
I decided the sender had failed and replaced it with a new identical one....you guessed it...after custom fitting the sender float as required making it non returnable...the problem was still there. OK...so its the gauge...? idiot...
Bought a new gauge...careful to not damage packing...and still does the same. Tried it with new wires from sender to either old or new gauge...still does the same....

Both the old and the new gauge just jump from rest to below E ...and dont indicate correctly.
My problem is I dont know how to test the sender or gauge...putting a multimeter on the sender shows about 250 ohms...but as it is supposed to be 300 empty and 30 full..? that doesnt sound right anyway...

The only thing which explains where I am to me is that I unnecessarly replaced a good sender...serves me right...and that the gauge is crook and I bought a crook one to replace it..? they are only cheap...

this feels to me like grasping at straws...but nothing else seems to fit the situation.

I need some advice on how to diagnose and how to test the gauge/gauges..? and/or the sender unit....either the one on the bench or the one installed...please dont tell me I have to take it out......

I am making tyhe connections as follows

S from sender to S on gauge
- from sender to GND on gauge

ignition live to I on gauge ( tests at 12.6V when ON)
ground to GND on gauge with - from sender unit.

Hope someone can suggest a way forward....Thanks folks.

[oldboot]

The first thing I would do is set up the units you have out of the boat, on the bench where you can see them.....wire them up and see how they behave.

Ya have to be connecting them wrong.

cheers

[Fed]

I've come across 2 types of senders & gauges that work completely opposite to each other.
By that I mean that one sender in the up position will drive the wrong gauge to the down/empty position and the same for the other mismatch.
This CANNOT be corrected by playing with the wiring you have to get the matching parts.
Have you tried it with the sender out of the tank, moving it up & down to see what happens at the gauge?

[Mindi]

well i have tried it on the bench ...and will try it again, but I am sure i have the same components that have been working for years..? will try the old sender on the bench with both gauges.
There is no way I can see it wrongly connected..? only 4 wires 2 of them GND ...one the signal other the ignition power source..?

[Fed]

Have had a Vthree/Teleflex universal sender in the tank and a Faria 2" gauge together OK for years but I didnt install them.

i have the same components that have been working for years..?
Sorry Mindi, I got the impression that it has never been connected and never worked, forget about the mismatched parts I mentioned.