changing rheostat type on fuel sender?

[JonE]

I've got an old front tank sender linked to what must be a late fuel gauge. I think thus it is working in reverse, so as you fill it the dial reads less.

Is it possible to change its [whatever] via simple wiring, so it will read correctly?

[Renaud]

The simplest way would be to do that mechanically, ie reverse the movement of the lever.

[JonE]

ok....but I'm having difficulty translating what I would need to do in practice..? i.e. what is achievable without the opportunity of buggering it up through lack of skill.

[wild_willy]

The sender rheostat  is no more than a coil of resistance wire. One of its ends is connected to earth (car's chassis via tank body) with the other end not connected to anything. Theoretically the earthed end can be disconnected and the previously non connected end connected to earth. This will reverse the electrical operation of the sender's rheostat.

Now depending on the mechanical arrangement of the particular sender will determine how  possible this rearrangement is.

[Renaud]

That's right Willy. It would be a perfect solution.
Then, disconnecting the earth connection could prove to be difficult.
If it is that kind of sender:



I still reckon it would be easier to cut or bend the lever and have it now at 180°.

[JonE]

ok - I'll get busy. Thankyou!

[Renaud]

My pleasure Jon!
It would be best first to verify the range of movement of the gauge's needle versus the lever amplitude; The drawback is that the sender's resistors can have very different values and yours be inadapted to your dashboard device.

[Nick Salmon]

This is always a useful reference: http://www.austin7.org/Technical%20Artic...20Working/

[Bob Culver]

Whatever you do proceed carefully. It always surprises me that this wiping electric contact, eventually with cut thru wires ,in close proximity to the tank vapour, does not lead to explosions.

[Renaud]

Come on Bob! There's only probably no more than 50 mA there.
Now, when I was around twenty I had a Austin mini with a terrific fuel pump continuously producing beautiful sparks right under the fuel tank. No leak allowed there!