BA Fairmont dual climate control. d/s all works great heater or air con, p/s regardless of temp setting only cold air. all vents & settings good just no heat p/s.

On my last fairmont heater would not get hot, took it to mechanic, he pressed climate control buttons for about ten seconds,(didn't pay attention, thought he was just checking it) heater was fine after. asked him what he did, he said he just reset it.
May be same problem, seems strange one side works perfect.