My 1984 300SD puts out 76 degree air at 65 mph on a 99 degree day with 40% humidity. Should it be colder than that? I am running the air conditioner at multilevel and the air is blowing through the defrosters, foot vents, and front panel vents. The blower is at high speed with the climate control set at min. It is also taking fresh air rather than recirculating the air. In the normal mode, the air blows through the defrosters and foot vents only.

What can I do to fix this?