Old fuel gauge (non 7), how does it work?

[OliverSedlacek]

I'm trying to get an 1955 vintage fuel gauge to read properly, but it's not obvious how it works. It looks like this, this and this. The terminal with the green wire goes to the sender, which is a variable resistor to chassis. Even when the sender is shorted out, the gauge still reads about 30%, when it should read empty.

 

The green and blue wires just go into the meter. Does anyone know how this works?

[tbird]

brain not fully functioning at moment but its not a 6 volt meter by any chance, if you are using 12 volts to test may explain odd readings, I think its been a long day

 

+v / -V volt issue

have you tried bunging a battery straight accross meter say start a 3V and work up to 6v and see how much deflection you get and which polarity drives guage positive

 

Edited by - tbird on 22 Aug 2009 21:27:42

[OliverSedlacek]

It's the original meter, and I tried it on a power supply. There must be something cunning in the design as the gauge doesn't move as you vary the supply between 12 an 14V.

[tbird]

possibly a sucking eggs situation here 😬 never worked with old fuel guages but new senders eg VDO the lower resistance at sender is the full reading around 3ohms to earth is full, around 200 ohms is empty, so low resistance at sender, max voltage accross meter = max deflection, so when you had 30% deflection of meter what voltage did you have accross meter, or is that where it was when you had 12 v accross it.

Pictures not ever so clear but I can see that both brass threads are isolated from earth, so presumeably the green wire connects to stud and then stud is connected to sender, what is the dohicky that the blue wire seems to connect to, it looks to be in the wrong place to be the meter coil