System 4 was cooling in conference room on arrival. Indoor coil has thawed. Indoor coil is clean. Insulation in return is damp from ice melt. Permanent 20*20 filter looks clean. Tech uploaded pictures of refrigerant pressures. Subcooling is measured at 10 degrees. Design subcooling is 13. Indoor coil temperature is about 36 degrees due to low outdoor temperature for cooling mode. Tech suspects filter may have been dirty. Cycled power and allowed system to cool for ten minutes. Uploaded running pressures. Found no challenges. Leak searched indoor coil. Found no refrigerant leaks. Changed blower from speed tap 2 to speed tap 3. Let Roger on site to clean washable filter every month and let us know if there are any further challenges. No charge for CMA follow up.