If it's the one in the centre towards the bottom of the dash it's to light up your heater controls. Did you take the bulb out yet? I found that the one in the rear defroster switch a match for Honda bulb #35505-SA5-003.
I just got my original owner's manual out of the glovebox where it's been for the past 36 years. The little light you refer to isn't a map reading light. It says in the manual..."Spot light to illuminate the heater levers between the front seats." I change my original bulb last year. The whole unit just pulls out. It is VW part #N177512.
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