Check whether any air is moving
Note whether every vent is dead, airflow is just weak, or only part of the house is affected. Also listen for the indoor blower. A quiet indoor unit points to a different diagnostic path than weak airflow from a running blower.
Look for filter, return, water, or ice clues
A clogged filter or blocked return can restrict air. Water near the indoor unit, ice on the line, or a safety switch clue can also explain why airflow changed. Take a photo if you see ice or water, then stop guessing at parts.
Use a diagnostic when the blower behavior is unclear
If the system is not moving air normally, starts and stops, or the outdoor unit runs while the indoor air does not, request the $95 Springfield Diagnostic. Scott can check the airflow, controls, and equipment behavior before repair pricing is discussed.