I have problem with my Air Condition,only blows in the side vent hot air. on 1994 Mercedes-Benz C280

Some time my Air Condition Control goes off went ,I am driving the it blows is not to hot but is not cold how suppost to be.I will like to fix that Thanaks.

Asked by for the 1994 Mercedes-Benz C280
sounds like a blend door isssue