nope i have a1.4 mk2 ph1 and it does it too.
i put it down to since i twisted my ariel and water went in. you guys have ariels in a different place though so it cant be that
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i have neons in my boot wired off the interior lighting. i did once wonder if there was a capicitor in the power supply to the neons conflicting with a capacitor in the fading circuit. but i dont know how the two would affect each other. power to interior lights fades and the neons are either on at a certain voltage, or off you see, maybe fecking up the current. dunno
dont know why people are banging on about the fan this is an electrical fault, it bakes a buzz when the light fades out after youve closed the door, completely unrelated.