An AC coil that freezes over in the middle of a Sacramento summer is either an airflow problem or a refrigerant-charge problem. The fix path is different for each.
If the filter is clogged or the evaporator coil is dirty, airflow drops below what the system needs to carry heat away from the coil. The coil temperature falls below freezing, moisture in the air freezes on contact, and now the coil is a block of ice. Shut the system off immediately — running a frozen coil stresses the compressor badly — and let the ice melt completely before restarting. Swap the filter, inspect the coil, and see whether the problem recurs.
If airflow looks good and the system still freezes, the refrigerant charge is likely low. Low refrigerant means the evaporator pressure drops and the coil temperature drops with it. This is a leak, not a 'needs more freon' situation — the refrigerant doesn't get consumed, so if it's low it's leaking out somewhere and needs to be found and repaired. Older R-22 systems that keep developing leaks are typically at the point where replacement beats repair.
A failed blower motor or a blocked return-air path creates the same no-airflow symptom and the same frozen-coil result.