Cool air falls toward the floor. Deflectors shouldn't be necessary unless the vent is behind a curtain or something, or if you want to deflect the cool air toward your easy chair.
Yes. You need to open the plumb, & you have an air vent there.
like deflectors on lorries
No. You vent air from a sewer line.
some lorries have deflectors fitted over their cabs, so it becomes more streamline, it can DEFLECT the air resistance too :) The Ugly Rat
An air admittance vent is a mechanical sewer vent which allows air to enter into the sewage system but does not allow exhaust of sewer gases.
To reduce the air resistance/drag acting against them and also to reduce the fuel consumption.
the air vent is cold
read your owners manual. i had to also. there is only two vent settings that will not use the compressor. the vent setting with the upper and lower vent showing will use the compressor.
An air vent is an opening, sometimes covered by a grate, which allows air to circulate around a room.
These are called deflectors in the parts catalogs the going across from drivers side to passenger side the part numbers are 10291967, 10291965, 10402904, 10291966
There may be something blocking the deflectors from sending air up there.