my car has to be at like 2 to 2 1/2 rpms or will stall y is this but ehen i read code it says manifacture?

I had similar problems with my 06 Taraus and was told by two diff people that i needed to replace the transmission which we all know is one of the most expense parts to replace. It ended up being a bad fuse in some sensor that told the car the transmission was about to go out so it would not shift gears or allow my ac to work. Easiest thing to do is get someone to hook it up to one of the machines that has the top fixes to which ever problem codes it says you have.