I have Casablanca fan/light, with a 4-button switch. Power and fan buttons work, but not the light button. Is the switch bad, or is the circuit board bad. How to tell?

Will

Start by testing the bulb in another fixture to insure its good, back to you

There is no clear way to tell other than replacing either the switch or the circuit board in the fan. These parts aren't cheap.

Some older models have a separate light module circuit board at the bottom of the fan.

I agree with checking the bulbs and wiring first.

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