I have a new installed York YP9C with all new duct work. I have the unit matched with York Communicating T-stat.

The furance seems to work fine, however, as the modulating furance is scaling up and gets close or at 100% the TSTAT shows an Indoor Equipment Error on the screen. When I dig into the menu system the error message says " Air Blockage Warning" -- This results in the another error in the T-STAT called Modulating Furance with a big red flashing icon.

Anyone have any idea what this error means?

Thanks in advance for your help.