When this occurs, it's generally caused by either a broken blend door or a partially clogged heater core. The blend door is the component in your heating/ventilation/air conditioning (HVAC) housing that regulates how much heat you get out of the vents vs. cold. Sometimes when they break, they don't evenly distribute the same temperature air across the left and right side vents. The heater core is the device in the dash that transfers heat from the engine coolant to the air in the passenger compartment. Often times when the internal coolant passages clog up, only half the heater core becomes hot. That's the side of the car blowing hot air.
A few quick questions though. Does your car have dual zone HVAC or only a single temperature control knob? Also, does the temperature change from hot to cool on the passenger side when you turn the knob?
Nov 3, 2019 at 1:45 PM