only have heat on passenger side, driver side blow cold air, modes change with no problem, does not have duel climate system
There are mode door actuators that control flaps that direct which way to direct air. There are other actuators that control flaps that direct either cold or hot air. The most likely cause is a faulty actuator. Second most likely cause is stuck flapper door. Third most likely cause is signal to the actuator is faulty (climate control module).