Here's why:
* Blend Door Actuator: This small motor controls the blend door, a flap inside your dashboard that mixes hot and cold air to regulate the temperature. If the actuator is failing, it might not be able to consistently position the blend door correctly. This leads to the fluctuating temperatures you're experiencing. The banging sound during sharp turns is likely the failing actuator struggling to maintain its position as the car's movement stresses the system. The forces from turning exacerbate the problem.
* Vacuum Leaks: Older Lincoln Town Cars often use vacuum lines to control the blend door. A leak in these lines can cause inconsistent temperature control, similar to a failing actuator. Sharp turns can shift the lines, potentially causing the intermittent temperature changes and possibly contributing to the banging sound.
* Other Possibilities (less likely): While less probable given the combination of symptoms, other issues could contribute:
* Faulty temperature sensor: An inaccurate sensor could send the wrong signals to the HVAC control unit.
* Wiring problems: Damaged or loose wiring to the actuator or sensor could cause intermittent operation.
* Low refrigerant (for AC): While less likely to cause the *alternating* hot and cold, low refrigerant can lead to inconsistent cooling.
What to do:
You need to have a qualified mechanic diagnose the problem. They can:
1. Inspect the vacuum lines: Check for leaks and proper connections.
2. Test the blend door actuator: This may involve visual inspection and/or testing its electrical function and range of motion.
3. Check the temperature sensor: Ensure it's providing accurate readings.
4. Inspect the wiring: Look for damage or loose connections.
5. Recharge the AC system (if applicable): If there's low refrigerant.
Ignoring the problem could lead to further damage and potentially more expensive repairs. The banging sound is especially concerning, as it suggests a part is loose or failing. Get it checked soon.
