York Furnace, M/N LY8S080A2UH11A, combustion blower turns on, no ignition of flame. 4 red flashes on control board.

Hi foutsbug, Four red flashes indicate that a 24-volt fuse or the high-limit switch is open. Possible causes include an improperly sized ducting system, a dirty air filter, a faulty blower motor, an open fuse on the control board or restricted circulating airflow. Good luck and let us know how it goes.

I checked fuse (good), Changed filter (dirty w/ pet hair- but I've seen worse), pushed resets on all limit switches switchs (none open). Unit did light again, though! Access panels were tweeked out. Thanks for the response though. Will keep you posted

Look for a sticker on the furnace, especially on the inner side of the fan compartment cover that discloses what the diagnostic codes mean.

The symptoms sound more like a pressure switch that isn't making, and a double check might be worth while.