1. Blend Door Actuator:
* What it does: This small motor controls a flap (blend door) that mixes hot and cold air. If the passenger-side actuator is malfunctioning, it might be stuck in the "hot" position.
* How to diagnose: This is tricky without specialized tools. You'll likely need to access the actuator (usually located behind the dashboard) and see if it moves freely when you adjust the temperature controls. A visual inspection might reveal a broken gear or other mechanical failure. You can sometimes hear a clicking sound from a failing actuator, especially when you try to change the temperature.
* How to fix: Replacement is usually the solution. You'll need to find the correct actuator for your model year and carefully install it, which often involves removing parts of the dashboard. This is an intermediate to advanced DIY repair.
2. Vacuum Lines:
* What they do: Older climate control systems often use vacuum lines to control the blend doors. A leak or blockage in the vacuum line supplying the passenger-side actuator will prevent it from working correctly.
* How to diagnose: Carefully inspect all vacuum lines connected to the climate control system. Look for cracks, disconnections, or kinks. A vacuum gauge (if you have one) can help pinpoint leaks. You can sometimes hear hissing sounds from leaks.
* How to fix: Repair or replace any damaged vacuum lines. Ensure all connections are secure.
3. Blend Door Linkage:
* What it does: The actuator operates a linkage that moves the blend door. This linkage can become broken, bent, or dislodged.
* How to diagnose: This requires accessing the blend door mechanism. Look for any broken or dislocated parts.
* How to fix: Repair or replace the damaged linkage. This often requires significant disassembly.
4. Mode Door Actuator (less likely):
* What it does: This controls the flow of air between the vents, floor, and defrost. A faulty mode door actuator *could* indirectly affect the temperature balance if it's preventing air from reaching the passenger side vents properly.
* How to diagnose: This is less likely the cause given your description, but if the other issues are ruled out, it's worth considering. Symptoms often involve the inability to change where air is directed.
Troubleshooting Steps:
1. Check the obvious: Make sure the passenger side vents aren't accidentally closed.
2. Listen for sounds: Listen carefully near the dashboard vents while adjusting the temperature controls. A clicking or whirring sound that is only present on the passenger side might indicate a failing actuator.
3. Consult a repair manual: A shop manual specific to your 1995 Buick Park Avenue will provide diagrams and instructions for accessing and repairing the climate control system. Haynes and Chilton manuals are good options.
4. Consider professional help: If you're not comfortable with automotive repair, this is a job best left to a qualified mechanic, especially if you have to remove part of the dashboard. Dashboard disassembly can be complex and easy to damage.
Remember to disconnect the battery's negative terminal before starting any work on the climate control system to prevent electrical shocks. Safety first!
