Driver side heater blowing cold air

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?

So you can change the passenger side from hot to cold then?

Okay. The next thing we need to do is remove the blend door actuator for the driver's side blend door. See the attached procedure. Once it's removed, you should be able to grasp the small gear on the housing(under where the actuator was mounted) and manually move the blend door from full cold to full hot(you should feel it hit a stop on both ends). While doing this, feel the air coming from the driver's side vents and see if it changes temperature accordingly. If you're able to change the temperature, the blend door actuator is most likely failed and needs replaced. Now if for some reason you don't feel the stops when turning the gear, the blend door itself is most likely broken inside the housing. If that's the case, the dash and housing will need to be removed from the vehicle to replace the door.

Let me know what you find!