faulty fuel gauge reading

[flaps7]

Since changing the fuel tank I have had problems with the fuel gauge readings. Gauge read ¼ full (when full) then after some weeks decided to read full (when not) and has stayed that way ever since.

 

I know nothing about electrics or how the gauges work or the meanings of what I have measured with a multimeter; not too sure I even know what I’m doing with the multimeter. I desperately need HELP.

 

Car currently has about ¾ of a tank. Resistance across the two terminals on the sender is 25; this figure would appear to be correct from all the fcuking about I did months ago. The voltage at the sender (green/black wire) is 3.9. Voltage at the gauge (green/black wire) is 3.9.

 

What should be my next step?

 

Cheers

Rick

 

 

[SM25T]

Sigma or K-series ?

From touring with other cars, the Sigma gauges often seem to be inaccurate .... showing 1/4 tank when tank known to be 2/3 full.

Are you happy with the position of the sender ? Could the float be contacting anything, thus preventing full movement ?

[flaps7]

There is unquestionably something dodgy with the reading, the needle is fully deflected. I am also pretty confident that the float is free as the measured resistance is about right for a 3/4 full tank.  

I live in Welwyn Garden and would ply food and drink to anyone who would be willing to offer on-site help.

Rick

[SM25T]

A full scale needle is usually a sign the sender wire is grounded to earth.

[F355GTS]

Could be a poor earth to the sender unit