RepairPal Certified shops can diagnose and repair your 1998 BMW 323is. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Even BMW's climate control systems are hugely complicated and computer-controlled, so it may be that kind of problem. I'd really recommend taking it to a BMW specialist for some diagnostics.
spend $1000+ at shop or dealer to have new computer put in & set. This you know and i detest these kind of useless answers.