from wot (little ) i kno is that if the windscrren has ever been out, then there may hav been a lack of silicon when it was replaced, this happen to a lot of mk 1 and mk2 GOtina owners, who hav had 2 replace their windscreens, can be remedied also by re-doing the whole process, but the rubber MUST b free of all old sealant and dust, to ensure a decent seal is achieved, but it has been 5 yrs since i did my 120y, and DIMLIGHTS option is way f#$%^n easier!