I have a attic/central air conditioner that is not sending cold air to one ceiling vent. I checked all of the vents with the thermometer and the temperature ranges from 62 F - 70 F. The temperature reads 80 at the problem vent. There is a strong flow of air out of this vent, as strong as the others. It is insulated in a similar way to the other pipes that service the vents, only it is just a couple of feet longer than the rest. I detect no air leakage.in the system. I opened up the "box" that all of the pipes connect to and although it is dirty in there, the air is 60 F and is flowing to all of the pipes. The inside air filter is new.
Why is one vent performing worse than the rest?
Thanks, Art