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I own a 95 sc400 not sure of Gen though car is new to me

Sc400 clicks when I press the brake pedal and the lights dim inside. Short story is I replaced an aftermarket stereo installed by previous owner and the lights front and rear. Now when I hit the brakes it clicks somewhere near the shifter and everything dims for a moment but it doesnt happen at night. Could it be the auto light sensor? And where can I find a manual or diagram for stereo qwiring that's reliable? Found a few online and some of the wiring matches but then some doesn't help......