Driver side heating

The heat on my passenger air vents works but
driver side does not it blows normal air when I
switch it to heat. The AC works just fine on both
sides but heat only on the passenger side. When I
switch the air flow to the defroster on the front for
heat on my windshield again the passenger half
will only blow heat and the driver side half will not.
When I need to defrost my windshield it'll only
defrost the passenger side not driver side and
passenger side will heat up but driver side won't. I
ruled out the controls being a problem cause if it
were the controls then I assumed my AC wouldn't
work on the driver side as well but it does so I
ruled that out.