Carrier 58MSA - 8 years old - experiencing code 2-1 "Gas Heating Lockout - control will not auto reset. Intermittently will shut down (give error code) and I have to reset power - this works sometime but not always. Over past 2 years have replaced limit switch and flame igniter. Have recently cleaned flame sensor.
Note that it is happening less frequently (twice a week) since I replaced brand new allergen filter with less expensive basic filter.
Any suggestions to trouble shoot or make mods would be appreciated. Thank you.