Three Potential Problems Resulting From Evaporator Coils Icing Up
1.If the ice becomes bad enough it can actually cause the tubing in the evaporator coil to collapse or break. This requires a service technician to repair and possibly a new evaporator coil will be needed or worse. As you can imagine this is an expensive fix.
2.Another problem with allowing your air filter to become this dirty is, equipment operating efficiency drops dramatically. The air conditioner will require longer run times to maintain space temperature and operating costs increase. You are much better off changing your air conditioner filters regularly.
3.There is also some risk of water damage when the ice melts. Often ice build up is bad enough to block drain openings and water overflows the condensate drain pan damaging walls, flooring and even ceilings if your air conditioner is located in your attic.