One of the potential issues I had in the choice of Stewart Warner gauges is the sender unit. The tank is pre made to accept smiths sender unit. I sourced a SW sender from the US on one of my trips so I have both. The question was, as the impedance from each sender is different, would the smiths unit allow the SW gauge to indicate the full range. I measured the difference of impedance and it was less than 15ohms at both end of the scale. I rigged up a circuit to check if the gauge would function.

Test circuit for SW gauge and Smiths sender

I am pleased to say that circuit proved the sender was suitable and work. This would allow me to fit the Smiths sender that the tank was fabricated to accept.

The sender unit operates with a float on a variable length wire. You need to adjust the length of the wire to match the tank depth. Once you have the length you solder the wire to fix it at the correct length.

This is one of those moments in the build that you hope you get right, if you haven’t you will be stripping out a lot of the car to fix the fault much later!

Soldered float wires to correct length

fully soldered

The final job was to make up the cable connections to match the SW wiring requirements, easy to do.

Finally the sender is fitted to the tank and ready to go in the car.

Smith Sender in situation