It isn't always as simple as replacing a bulb. The wires could be corroded and not work properly. And it definitely matters if the bulbs work as well. They cost money to replace. I'm wondering if they have been hooked to power and light up?
I found a handful of these mixed in with a box of vintage automobile thermostats that I bought. The knob says "Alcohol Low High." Does anyone know if they are actually auto parts and what their use is? Thanks