Originally Posted by j free
They sell heater duct blockers that are 10 by 16 inch magnetic strips that you can cut to size and place over vents to detour flow to other vents. They come in white and brown and run approx. $14 for two at camping world. What's great about them is you can cut them so you can still allow a little heat in the area your blocking from.
My registers were plastic so that wouldn't work for me.
I went to Lowe's and bought replacements with a dampener.
The new ones are metal but with the dampener, I don't need the magnetic mats.
That helped and I also repositioned the ducts on the furnace to improve air flow to the back of the unit.
Partially closing the one that blew on the t/stat helped too but I suspect at some point I'll have to drop the coroplast (underbelly) and see what horrors I might find there.