Throwing the same 4 blinking light code for Open Limit Switch. I cleaned the flame sensor, even replaced the limit switch with a new one. Replaced the filters.
Inducer fan kicks on, pressure switch closes, ignitor glows red and flames light, the motor fan kicks on and blows for 10 minutes or so, then the flame goes out and throws the code. I need to see if there is a secondary limit switch somewhere. Nights aren't too bad, outside gets down to the 40s and the house gets down to 67 or so, not s real threat of freezing anyone out yet, LOL. I might just bresk down and pay the service fee, to find the real problem......damn it.