Arrived on site for heating maintenance. Turn thermostats on heating to make sure units run normally, units were running. Turned the units off to operate on the unit safely. Removed flame sensor of all the units to clean them thoroughly. Exchanged all the filters for every unit with new filters. Check the belts on all units, but we're in good condition. Cleaned the area where the swing sensor is with CO2 cartridges making it as clear/ clean as it could be. On one of the units when the you know what's going for he the flame was stuttering. Only two out of five Flames appeared before cleaning the flame sensor and ignition, after cleaning both flame and ignition unit was working normally. Burners for running behind the thermostat wiring on the control board or corroded. Cut the corroded part of the thermostat wiring for a brand new clean and tight connection under control board you're avoiding any possible thermostat communication to the control board issues later on.
