Will cleaning glass with isopropyl alcohol remove my rain repellent?

It can weaken it over time. Isopropyl alcohol is a solvent that is often used to prepare glass before a coating is applied, and regular use on treated glass can gradually reduce its water-repellent effect. For routine cleaning of treated glass, use a mild, ammonia-free glass cleaner or plain water and a clean microfiber. Keep alcohol-based cleaners for preparation before reapplying the treatment.