A/C only blows out far left dash vent

[KB'sF350]

A/C started blowing, in dash mode, only out of for left vent. I can change to defrost and floor but on dash only the left vent is blowing air and very hard.

 

[TARM]

You have a vacuum leak. If you have auto hubs check there first. Next check the vacuum pump. Its a very common issue and easy fix.