I have a forced air heating system in my house. It has 5 lower level heating vents and 8 upper level vents. I have attached a diagram showing where each one is located in the house and the path it takes from the main duct. The furnace is on the upper left end of the main duct pictured. The heat comes out of each vent very well with the exception of the one in the lower left corner of this diagram. The corner bedroom. We have a finished basement but I have crawled in the ceiling down there and detached that vent from the main line looking for any jam but it just does not seem to get the same air flow as all the other vents.

Can anyone explain why this would be and what I can do to fix it?

Thanks,

Has the duct work to that vent become disconnected?

No, I have crawled to it before to check for blockage. In doing so, I disconnected it from the main duct, checked everything, and then re-fastened it. The duct itself seemed fine. There is some air movement through it but very little.

Did you have strong air flow when you disconnected it from the main trunk?

No, I really didn't. Just seems like it's in the wrong spot on the main duct but that shouldn't matter when it's forced air should it.

The duct in question actually comes off the main line right after the main curve. (above the opening to the basement) It comes out of the top of the duct, turns 90 degrees to the back, goes about 12 inches, then turns 90 degrees to the right, goes about 10 feet, then turns 90 degrees again, and goes to the back wall of the house.

Could there be a problem with it coming out the top of the main duct instead of side or bottom like the others? Problem being right over the basement vent? Problem having too many turns?