There's four pair, brown, brown white, and two pair of grey brown. There's four tabs on the switch, but what goes where?

I guessed the two pair of grey brown on one side of the switch and the other two sets on the other side?
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One pair operates the interior light, and the other pair operates the warning buzzer for key still in the ignition. Unless you want the warning buzzer to still operate, you can just forget those two wires. The red wires feed the buzzer, and the brown ones run the interior light. If you do kiss off the buzzer circuit, you can replace the switch with the same part used for the parking brake warning light switch down near the parking brake lever.