ohms/Fuel Gauge and Sender

[mocass]

Hi Folks. In my Truck which is a 1964 Chevrolet C10, I have a Fuel gauge that is rated at 90 ohms, In the fuel tank I have the Fuel sender that is rated at 30 ohms, This gives a wrong reading as when the fuel tank is full the gauge shows half full.
For my truck there is no 90 ohms sender I can buy that fits this particular model of tank.
My question is, I am told that there is a way of fitting a resistor to the sender that alters it from 30 ohms to 90 ohms, [matching the fuel gauge]
Can anyone tell me what resistor I need and how to fit it please. hope you can help.

 

[Alec_t]

Welcome to EP!

I am told that there is a way of fitting a resistor to the sender that alters it from 30 ohms to 90 ohms

Unfortunately it's not as simple as just fitting a resistor.
Assuming the higher the fuel level the higher the sender resistance, then if you were to connect 60Ω in series with the 30Ω sender the total resistance would be 90Ω and a full tank would read correctly on the gauge. However, with an empty tank the total resistance would be 60Ω, which would read as though the tank were about 2/3 full .

 

[Harald Kapp]

Welcome to EP.

Normally a simple resistor will not work as expected. You can increase the max. resistance to 90 Ω by adding a 60 Ω fixed resistor to the 30 Ω sensor. However, the fixed resistor will also increase the sense value for low fuel and your gauge will show the tank being half full when in fact it is empty.

Have a look at this thread, maybe the answer is there. The guy seemed to get it working with an adjustable resistor (potentiometer) and probably some good luck.

 

[Harald Kapp]

Arrgh Alec, you beat me by just 1 minute