Homeowner stated that the unit is not keeping up with the temperature set at the thermostat (2 zoned system,,gas) Based on information from the customer we started at the indoor unit,,, measured temperature differential,, had 13 degrees split differential between return and supply plenums,, inspected return filter,, had just been replaced,, checked refrigerant pressures ,,found the unit low on refrigerant,,unit is running with R410A refrigerant ( no longer made) unit is 10 years old and out of warranty,, at this point we recommended to replace the full system because we don’t know if there’s something else going on with the unit.