I have a dodge caravan. The battery light came on a week ago and then a few hours later everything shut down while driving it.I cleaned the battery terminals because they were caked with corrosionbut that didnt do it.I took the alternator out, took it and haqd it tested but it showed everything to be ok.I put the alternator back in and no battery light.I drove it all day and that night it happened again.A friend suggested the electrical part of the ignition switch.I cant afford a mechanic so id like to fix it myself. Any ideas on what the problem may be?Please, any help would be grately appreciated.
Replace the brushes in the alternator. The worst way to test it is by removing it from the engine. They almost always test "good" that way. Any testing has to be done while the problem is occurring, and that's when the "battery" light is on.
The brush assembly costs around nine dollars, and I can describe how to replace it. There ARE other things that can cause intermittent charging, but once the alternator is already off the engine, you might as well just pop the brushes in. On older models that could even be done without removing the alternator from the engine.
As for the corrosion on the battery terminals, that is a very good sign the battery is going to fail in the next six months.