* Blend Door Actuator Malfunction (Driver's Side): The blend door is controlled by a small electric motor called an actuator. If the driver's side actuator is malfunctioning, it might be stuck in a position that only allows hot air to flow to that side, even when you select AC. The passenger side actuator is likely working correctly.
* Blend Door Linkage Problem (Driver's Side): The actuator might be working, but the linkage connecting it to the blend door itself could be broken or dislodged. This prevents the blend door from moving correctly.
* Vacuum Leak (Less Likely): In some older vehicles, vacuum lines control the blend doors. A leak in the vacuum line supplying the driver's side could prevent the blend door from moving to the correct position for cold air. This is less common in modern vehicles with electric actuators.
* Faulty Temperature Sensor: A malfunctioning temperature sensor could be sending incorrect signals to the HVAC system, causing it to only send hot air to the driver's side, regardless of the setting.
What you should do:
1. Check your vehicle's manual: See if there's any information about diagnosing HVAC issues.
2. Inspect the HVAC controls: Make sure the temperature controls and fan speed are working correctly.
3. Consult a repair manual or a qualified mechanic: This issue requires a deeper investigation to pinpoint the exact cause. A mechanic can diagnose the problem and determine whether it's a faulty actuator, linkage, vacuum leak, or another component.
Important Note: Attempting to fix this yourself without proper knowledge could damage your HVAC system further. It's best to seek professional help to avoid costly repairs.
