Most Likely Culprits:
* Poor Ground Connections: This is the most common cause of intermittent electrical problems. Corrosion on ground straps or connections can cause inconsistent power delivery and erratic behavior of various components. Check all ground connections near the battery, engine, and body. Pay close attention to the ground straps themselves; they may need cleaning or replacing.
* Alternator: A failing alternator might not be providing enough power consistently. Test the alternator's output voltage while the engine is running. It should be around 13.5-14.5 volts. A low voltage reading points to a failing alternator or a problem with its wiring.
* Battery Cables: Check the battery terminals and cables for corrosion and looseness. Clean them thoroughly with a wire brush and baking soda solution. Replace cables if they show significant wear or damage.
* Fuse Box: Inspect the fuse box(es) (under the hood and potentially inside the van) for blown fuses or corroded contacts. Pay special attention to fuses related to lighting, instruments, and the ignition system. Replace any blown fuses, but investigate *why* they blew before simply replacing them.
* Wiring Harness: This is a more complex issue. Damage or corrosion within the main wiring harness can cause intermittent problems like the ones you describe. This is difficult to diagnose without specialized tools and electrical diagrams. Look for obvious signs of damage to the wiring, such as chafing or melted insulation.
* Ignition Switch: A failing ignition switch can cause intermittent power loss to various systems. This is less likely to cause *all* the symptoms you describe, but it's possible.
* Body Control Module (BCM): The BCM controls many electrical functions in the van. A faulty BCM can lead to a variety of strange electrical problems. Diagnosis of a BCM issue usually requires specialized tools and knowledge.
Troubleshooting Steps:
1. Check the Obvious: Start with the easiest checks: battery cables, fuses, and ground connections. Clean or replace any faulty components.
2. Test the Alternator: Have the alternator tested at an auto parts store or use a multimeter to check its output voltage.
3. Visual Inspection: Carefully inspect the wiring harness for any visible damage.
4. Systematic Testing: If the above steps don't reveal the problem, you might need a multimeter to systematically check the voltage at various points in the electrical system. This requires some electrical knowledge or the assistance of a mechanic.
5. Professional Diagnosis: If you're not comfortable troubleshooting electrical problems, it's best to take your Astro van to a qualified mechanic or auto electrician. They have the tools and expertise to diagnose the issue accurately.
Important Note: Driving with intermittent brake lights and turn signals is extremely dangerous. Do not drive the van until the problem is resolved. This could lead to accidents.
