I. Safety First!
* Disconnect the negative battery terminal (-) before you start any testing. This prevents accidental shorts and protects you from electrical shock.
* Wear safety glasses. There's a chance of battery acid splash or something else flying around.
II. Visual Inspection:
1. Look for obvious damage: Check the alternator for any physical damage like loose belts, broken or frayed wires, corrosion on terminals, or any signs of burning or melting.
2. Examine the belt: Make sure the serpentine belt (or V-belt, depending on your model) is properly tensioned and not cracked, glazed, or worn. A slipping belt can prevent the alternator from charging properly.
III. Electrical Testing (requires a multimeter):
You'll need a multimeter capable of measuring both voltage (DC volts) and current (amps). Auto parts stores usually rent or sell them inexpensively.
1. Check battery voltage (engine OFF): Connect the multimeter to the battery terminals. You should see around 12.6 volts. Lower than 12 volts indicates a weak battery, which can mask alternator problems. A significantly lower voltage could indicate a bad battery that needs replacing before further alternator testing.
2. Check battery voltage (engine ON): Start the engine and let it idle. The voltage should rise to between 13.5 and 14.5 volts. A reading below 13 volts suggests the alternator isn't charging properly. A reading significantly above 14.5 might indicate a problem with the voltage regulator.
3. Check alternator output (engine ON - more advanced): This step is more involved and requires some electrical know-how. You need to disconnect the alternator's output wire (usually a large wire going to the battery or a battery-connected bus bar) and measure the amperage with the engine running. *Caution:* Be extremely careful doing this to avoid shorting anything. You are measuring a relatively high current. It's best to consult a wiring diagram for your specific vehicle to correctly identify this wire. Ideally, you would also monitor the voltage while doing this to see if the voltage changes as the load increases. A good alternator should show a significant output current.
IV. Interpreting Results:
* Low voltage (both engine OFF and ON): Indicates a bad battery.
* Low voltage (engine ON only): Points towards a faulty alternator, a bad voltage regulator (internal to the alternator in many cases), or a problem with the wiring between the alternator and the battery.
* High voltage (engine ON): Suggests a problem with the voltage regulator within the alternator.
* No change in voltage (engine ON vs. OFF): Definite alternator issue.
V. Troubleshooting:
If the tests reveal a problem, the alternator might need repair or replacement. Consider these possibilities:
* Bad alternator: The most likely culprit if voltage is low with the engine running. Replacement is often the easiest solution.
* Bad voltage regulator: This is a component *inside* the alternator. Some alternators have replaceable regulators, while others require replacing the entire unit.
* Faulty wiring: Damaged or corroded wires can prevent proper charging. Inspect all wiring related to the alternator.
* Slipping belt: A worn or loose belt will prevent the alternator from spinning correctly, reducing charging.
Important Note: While these steps are generally applicable, the specific location of components and wiring may vary slightly depending on the exact year and model of your '85 Chrysler Fifth Avenue. Consulting a repair manual specific to your vehicle is highly recommended for detailed information and diagrams. If you're not comfortable working with car electrical systems, it's best to take your car to a qualified mechanic.
