Bravo Keygrip!
High Wing Drifter, what you can say for sure is that the light isn't on when it should be on. That's important because that leads directly to the next question: 'Why?'
Then comes the fault finding. Is something causing a the light to be dim? In a Piper that would be the nav lights are on, in a Cessna the 'eye' on the light is closed. Is the bulb blown? Swap the lights around. Maybe it's the consequence of another system's problem eg alternator failure & flat battery. Is the gear really down? Did you really move the lever like you thought - or forgot. Use whatever equipment is installed to verify eg mirrors, mechanical indicators, LOOK(!) and of course the alternatate extension mechanism(s).
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4. Corrosion resistance