Q: Having issue with HVAC system in my car

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I'm having an HVAC problem with my car. When I turn on the heater, it blows hot air on the driver's side; however, the passenger side blows cold air. This happens even if the passenger zone button is not selected. I tried switching to the vents to blow on the floor, and it does the same thing. I think this might caused by the blend door actuator. Is that possible? If so, is there write-up on how to replace it?

This symptom can actually be caused by two different things. You are right to think that the blend door actuator could be at fault. If the blend door is not able to move, this will not allow air passing over the heater core to enter the passenger side of the vehicle as most systems default to expose the evaporator.

Another possible cause of this issue would be the dual zone climate control valve or the heater control valve depending on the manufacturer. If the passenger side of the valve is not opening to its full capacity, the amount of coolant that reaches the passenger side heater core will not be as much as what reaches the driver side. This would explain the major temperature difference.

I would recommend having a professional inspect your HVAC system to locate the faulty part and get your heater working correctly again.

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