Chattering relays is a common sign of a run-down battery. In this case, given the symptoms and mileage, I'd be suspicious of a failed diode in the alternator. With that, the most current the alternator will be able to develop is exactly one third of its maximum rating. That may not be enough to run the entire electrical system under all conditions. The battery will have to make up the difference as it slowly runs down over days or weeks.
One easy thing to start with is to charge the battery slowly for a few hours, then see if the symptoms change. Next is to perform a charging system test, but you need a professional load tester for that. You can start the testing yourself with an inexpensive digital voltmeter. Measure the battery voltage, first with the engine off. It should be close to 12.6 volts. If it is closer to 12.2 volts, it is good but discharged. If it's around 11 volts or less, it has a shorted cell and must be replaced.
Next, measure the battery voltage again with the engine running. Now it must be between 13.75 and 14.75 volts. If it is, that only means it is okay to continue with the professional tests. The least effective way to do that is to remove the alternator for a bench test. The best way is to take the van to a shop with the tester. In addition to the test you just did, they will also test for "full-load output current" and "ripple" voltage. Those are indicators of a failed diode.
Also common at the mileage you listed is worn brushes in the alternator. Those always start out as an intermittent failure to charge, often for just a minute or two, but those periods of failure get longer and longer, often over many months. If the testing is able to be done while the problem is occurring, battery, (system) voltage will stay too low, as in close to 12.6 volts. I can describe tests for worn brushes, but to be valid, that testing has to be done with the engine running, and while the problem is occurring. If testing points to worn brushes, most people replace the alternator, but it is not terribly difficult to replace just the brush assembly. I did that on my '94 Grand Voyager without even removing the alternator from the engine. I can go into more detail with that if it comes to that.
Let me know if you do this test and what you find.
Sunday, December 14th, 2025 AT 5:00 PM
