I have a York Furnace Model#: GY9S080C16DH11H with Serial #W0F5302743. I replaced the air filter and the unit started, but then quit after about 5 minutes. The small fan kept running. I opened the panel and the little light (usually green) was flashing (red) 4 flashes (meaning limit sw. open) and then 11 flashes (meaning limit se. open - Blower failure).
I have been told that there is a limit sw. that I can reset, but can not find it.

First off does the blower run? While the control board is flashing 4, or if you turn the t-stat to on? If yes then look for the high limit.

http://store.hamiltonhomeproducts.com/ProductImages/limitswitches/025-29041-005.jpg

It will be located above the burners. Turn the power off remove this limit and wipe the dust off it and give it a few small taps. Then reinstall and try the furnace again