1. Wiring and Connections:
* Alternator Output Wire: The wire connecting the alternator's output terminal (usually a large, heavy gauge wire) to the battery's positive (+) terminal might be broken, corroded, loose, or have a poor connection. Inspect this wire thoroughly along its entire length, checking for breaks, corrosion, and secure connections at both ends. Pay close attention to the connection points – any corrosion here will significantly impede current flow.
* Battery Cables: Check the positive (+) and negative (-) battery cables for corrosion, looseness, and damage. Clean the cable terminals with a wire brush and baking soda solution if needed. Make sure the connections are tight and secure.
* Ground Connections: A poor ground connection can prevent the charging system from working correctly. Find the ground wire from the engine block to the chassis and ensure it's clean and tightly connected. There might be other ground wires related to the charging system; check those as well.
2. Voltage Regulator (Internal or External):
* Internal Regulator (Most Likely): Even if the alternator tests good, its internal voltage regulator might be faulty. This component controls the alternator's output voltage. A faulty regulator can prevent the alternator from charging the battery properly. Testing the voltage regulator requires specialized equipment and might be beyond a DIY level. Replacement is often simpler than testing.
* External Regulator (Less Likely on a '92 Park Avenue): Older vehicles sometimes had external voltage regulators. If yours does (check your alternator and wiring diagram), inspect it for damage and connections.
3. Battery Itself:
* Bad Battery: A severely sulfated or otherwise damaged battery might not accept a charge, even if the alternator is working. Have the battery load tested at an auto parts store to determine its health.
4. Fuses and Circuit Breakers:
* Check the Fuse Box: There might be a fuse or circuit breaker specifically protecting the charging circuit. Consult your owner's manual to locate the relevant fuse(s) or breaker(s) and check them for continuity.
Troubleshooting Steps:
1. Visual Inspection: Start with a thorough visual inspection of all wiring, connections, and components mentioned above.
2. Voltage Testing: Use a multimeter to check the voltage at the battery terminals:
* Engine Off: Should read approximately 12.6V (a fully charged battery).
* Engine Running: Should read 13.5-14.5V. If significantly lower, it points to a charging system problem.
* Voltage at Alternator Output Terminal (Engine Running): Should also be 13.5-14.5V. If significantly lower than the battery voltage, there is a problem between the alternator and the battery.
3. Load Test the Battery: Take the battery to an auto parts store for a load test to rule out a bad battery.
Important Note: If you're not comfortable working with car electrical systems, take your Buick to a qualified mechanic for diagnosis and repair. Incorrectly diagnosing and repairing electrical issues can be dangerous.
