Oh, just in case you don't know. When you reach the limit of travel on the multiturn pot, they don't stop, you will hear and feel a faint click as the internal drive sort of ratchets past the wiper end. no harm, turn the opposite way.
Drawing didn't come out so good. let me know if I need to clean it up and resend. I looked up some VDO fuel gauge stuff quickly, looks like "zero" is actually 10 -20 ohms or so and the other end is 180 - 230 ohms or so. I wouldn't imagine the Alfa one would be too far off from one of those. But you never know.
| ^ | ---connect to one of the ends
|---connect to the "wiper"
resistance will change as the wiper moves along the internal resistance.
You may be able to add a shunt (a parallel resistance to the gauge resistance providing a path for some of the current to bypass the gauge leaving the correct amount to operate the meter as expected) to a VDO gauge to compensate/adjust for a difference in input resistance.
Just saw that I had two messages, I hope this is replying.
I don't know what empty ohms is equal too. And I am about 2400 miles from my car
What you can do is get a variable resistor, 10 turn, 20 turn, etc from radio shack. the fuel gauge is just an ammeter. so if you connect the multiturn potentiometer with one leg to the fuel gauge and the wiper to ground you will see the gauge change as you add resistance to the circuit. When the gauge reads full, remove the potentiometer and measure the resistance. this will get you rather close.
hello, i noticed you post on the ' fuel gauge' problem.. a question.. do you know the ohm's reading from empty to full on a 84 spider gauge?i guess they should be all the same, as the sender did not change all those years.. i am doing a re-design of my dash. centre counsel. on my alfa i have 3 vdo gauges now oil pressure volt, and tmep. ( oil) ( water will be the same) but i really want all my minor gauges to look alike. i will just live with the speedo/tack being a diff back light.