Fasting Belts reactivate + Expand air-conditioning sensor fans

Hello dear people. am a very fresh saab driver (purchased used yesterday). decision fell on a 900er 2.0 turbo and so far everything is technically in best order, optically smaller defects. my previous owner probably had the same problem as this master and had the belt reminder deactivated. but now I want to know how to fix it again. apparently there is something brimmed, since the belt lamp lights up at the start check. someone ne idea? the second would be that the air he (habe klimaautomatic), who pushes the air to the sensor, probably has a small defect, so he grinds. also read that sometimes a prize wd-40 causes wonders and if not, you can also switch. unfortunately, however, nobody tells me where exactly that sits, or how I get all this up?!? doesn’t want to destroy anything. one last small question still : the light switch for standing or driving light, is the light illuminated? with me it is dark… thank you already lg