MotoMeter Temp Gauge

[Stan]

My car has a Boyce MotoMeter Temp Gauge mounted on the steering column. There are two wires out the back of the gauge. One is clearly the temperature measurement and it is tied into the water side. The other wire is not connected but looked like it may have been tied to an electrical supply. Does anyone know what this is for and how it should be connected? All comments appreciated.

 

[Jim Boehmke]

there's a light bulb inside the case.

 

[HoarseWhisperer]

My car has a Boyce MotoMeter Temp Gauge mounted on the steering column. There are two wires out the back of the gauge. One is clearly the temperature measurement and it is tied into the water side. The other wire is not connected but looked like it may have been tied to an electrical supply. Does anyone know what this is for and how it should be connected? All comments appreciated.

Does it look like this one?