Upon arrival I completed diagnostics and found that system has 2 returns with 2 electric filters. I pulled filters and they looked okay. I went to outdoor unit and noticed that unit wasn’t running. I found that disconnect was in the off position. I turned disconnect around and gauged up on a/c. Temp split was as 20 (61/41) pressures were 80/257 SH-20 SC-12/15. When tech put filters back in suction side dropped to 68. Tech noticed that a/c was freezing up outside. After trying to get airflow figured out we found a fire damper closed within the duct work Need to repair damper and return to install damper.