York diamond 80 burners ignite shut down 3 times give 7 blink code
unit ignites 3 times shuts off with 7 blinking led code. Fame sensor replaced less then 1 year ago. cleaned flame sensor unit with pencil eraser (doesn't damage like steel wool or sandpaper) runs fine for two three days then back to error. no blockages in intake air/ vent air. had service tech out 6 months ago and found no issue with combustion air, gas pressure.
CO2 % 6.3.
O2% 9.8
CO PPM 21 burners and ignitor checked cleaned and all in great condition. Pressure switch?
nothing shows what the voltage or ohm should be for the pressure switch located in upper left hand corner.