Owner's Problem Description
The owner of a 2000 Dodge Caravan reports that the vehicle won't start and exhibits a chattering sound from the Automatic Shutdown Relay (ASR) after charging the battery. They suspect a bad alternator since the van ran on battery power. The chattering occurs steadily when the ignition is turned on, leading to questions about whether the relay is functioning properly. Previous attempts to start the vehicle were unsuccessful.
Professional Technical Analysis
The 2000 Dodge Caravan, equipped with a 3.3L V6 engine and an automatic transmission, has been reported to have starting issues, with the owner noting a continuous chattering from the Automatic Shutdown Relay (ASR) when the ignition is turned on. The vehicle, having been previously powered by the battery alone, raises concerns about the alternator's functionality. In normal conditions, the ASR should momentarily activate upon ignition, allowing power to the fuel pump, ignition coil, and other critical components during engine cranking. If the relay is chattering steadily, this can indicate insufficient voltage supply, often stemming from a weak or discharged battery or a failing alternator. The ASR requires a voltage range of 12V-14.5V for proper operation, and if the voltage falls below this range, it may chatter due to insufficient power. A thorough inspection of the battery's state, including voltage checks (a healthy battery should read around 12.6V at rest) and load testing, is essential. Additionally, the alternator's output, which should ideally be between 13.8-14.4V during operation, must be evaluated to ensure it is functioning correctly. Given the prior history of the vehicle running solely on battery, the likelihood of a failing alternator is high, especially if the battery shows signs of deterioration. Furthermore, the chattering ASR could also suggest an underlying electrical issue affecting the power distribution, warranting further diagnostic steps. Safety concerns arise as a failing charging system can lead to complete vehicle shutdown, emphasizing the need for immediate attention.
Possible Causes
Most common causes (ordered by frequency):
- Low Battery Voltage: If the battery voltage falls below 12V, the ASR may chatter due to insufficient power supply. A fully charged battery should maintain a voltage of approximately 12.6V. Conduct a voltage test at the battery terminals and load test the battery using a load tester to ensure it can hold charge under load. If the battery fails to maintain voltage, it may need replacement. - Battery voltage below 12V during testing, poor cranking performance, battery age over 4 years indicating possible wear.
- Faulty Alternator: A malfunctioning alternator may not charge the battery adequately, leading to voltage drops. This can be tested by measuring the alternator output at idle (should be 13.8-14.4V). If the output is insufficient, it may indicate a failed voltage regulator or internal alternator failure. - Alternator output voltage reading below 13.8V, visible wear on alternator components, unusual noises from the alternator.
- Automatic Shutdown Relay Failure: The ASR itself may be malfunctioning, leading to its chattering. Test the relay's operation by applying direct power to it and observing if it activates correctly. Measure the relay coil resistance (should be around 60-80 ohms). If the relay fails to operate correctly, it should be replaced. - Relay chattering consistently, direct power test shows relay does not activate, resistance measurement out of specification.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Battery Voltage Test: Start by checking the battery voltage with a digital multimeter. Ensure it reads at least 12.6V. If the voltage is low, perform a load test to determine if the battery can maintain voltage under load. If the battery fails, replace it with an OEM part (MOPAR P/N 04868023AA) or quality aftermarket equivalent.
- STEP 2 - Alternator Output Test: With the engine running, measure the alternator output voltage at the battery terminals. It should read between 13.8-14.4V. If the output is below this range, inspect the alternator connections and consider testing the alternator with a load tester. Check for proper grounding and examine the B+ terminal connections for corrosion.
- STEP 3 - ASR Functionality Check: Test the ASR by applying direct voltage to its terminals. It should click and operate correctly. Measure the resistance across the relay terminals; it should be between 60-80 ohms. If it fails this test, replace the ASR with a new unit (MOPAR P/N 56028361AA).
- STEP 4 - System Voltage Monitor: Utilize the GeekOBD APP to monitor the vehicle's voltage and system parameters during cranking. Watch for any fluctuations in voltage and document any irregularities. This data will assist in diagnosing any intermittent issues.
