Here's why:
* Blend Doors Control Airflow: The blend doors are flaps inside your HVAC system that regulate the mixture of hot and cold air. They're controlled by actuators – small electric motors.
* Separate Actuators: In most cars, including likely your Lincoln LS, there are separate actuators for the driver's side and passenger's side. If one actuator fails or is malfunctioning, it can prevent that side from receiving the correct temperature blend. A malfunctioning actuator might be stuck in the cold position (driver's side in your case), or not receiving power.
* Other Possibilities (Less Likely):
* Vacuum Leaks: While less common in this system (as it's likely electronically controlled), vacuum leaks in the HVAC system *could* affect blend door operation. However, blend door actuators are the more typical suspect.
* Faulty Temperature Sensor: A faulty sensor might provide incorrect temperature readings to the climate control system, leading to improper blending.
* Wiring Issues: Damaged or corroded wiring to the actuators could prevent them from working correctly.
* Blend Door Linkage: Rarely, the mechanical linkage connecting the actuator to the blend door itself could be broken or disconnected.
Troubleshooting Steps:
1. Check the HVAC Control Panel: Make sure the controls are set correctly for both sides to receive heat.
2. Listen for Actuator Sounds: When you change the temperature settings, listen carefully near the HVAC system (under the dash) for the clicking or whirring sound of the actuators. One may be silent if it's faulty.
3. Visual Inspection (Difficult): Accessing the blend doors and actuators in a 2000 Lincoln LS requires partial disassembly of the dashboard. This is best left to a mechanic unless you are experienced with car repair.
4. Diagnostic Scan: A professional mechanic can use an OBD-II scanner to check for any climate control system codes. This can pinpoint the exact problem area.
Recommendation:
Given the symptoms, a malfunctioning blend door actuator (driver's side) is the most probable cause. Taking your Lincoln to a qualified mechanic for diagnosis and repair is recommended. Replacing a blend door actuator is usually a manageable repair for a mechanic, although accessing it can be challenging.
