Auto Electronics: 3-wire H20 temp gauge, oldsmobile delta 88, temperature gauge

Question
I have a 1966 Oldsmobile Delta 88 and wanted a blue lit water temperature gauge (non-digital).  I found one with 3-wires.  A Mechanic told me it wouldn't work on my car.  Is there not a sensor that would work on a classic car?  A sensor on the car has only one terminal, but nothing attached to it.  I think I got the gauge from a website called JM Performance two years ago, which I haven't found online now.

Answer
Hi Carl.
Most gauges (aftermarket and factory) use only one wire sending units threaded on the block, head or water outlet, except newer vehicles which use a 2 terminal type monitored by the computers.
You should be able to use that gauge you have, you are saying it is lighted so that means the other 2 cables should be your power and ground for the light.
Please understand that without having the specific info on the gauge I couldn't be 100 % sure, but most gauges work this way.