Аmerican standard error code 79
This code appears when the system recognizes the low pressure switch as open. This may be due to bad coil or filters (blocked by debris), or lack of refrigerant. Try resetting the system by turning of and on the outside and inside units. Check the coil and the filters. If they are good, check the refrigerant level and charge the unit, if necessary.
American standard thermostat error code 126
If you see the 126 code, you need to reset your unit. Turn off the inside and outside units. Also, you should check the inside unit’s float switch (located on the drain line). There you will see two wires leading to it. This code also appears when the float switch is tripped.