When turning heater on the fire ignites and the vent blower to outside is on. The main blower to circulate air throughout house is on and turning, yet does not seem to be moving any air. When taking the cover off there does not seem to be any noticeable air flow in chamber either. The filter is clean and passageway is unobstructed. It is almost as if the main blower is going way to slow. Same situation for Air conditioning. The furnace is a York Diamond 80. Please Help