The alternator died around 155k. Replaced it and it was fine until last week. Changed it again and now the battery light is on again. Had the battery checked and they siad it was fine. What could cause the alternator to continuously fail? Everything is connected just fine and their are no liquids spraying or dripping.
Check the ground cable between the engine and chassis. Also check wiring to the alternator for corroded connections, especially the thin sense/exciter wire. (I've had that happen. A thin wire to the alternator looked good but due to corrosion wasn't working. It fell apart at the crimped connector with a little wiggling. The corroded connection was preventing the alternator from working.)
Alternator output on the car is probably controlled by the ECU (most are since late 1990s) and that could be defective after 17 years.
It's also possible that the replacement alternators have been defective. The quality of replacement parts in recent years has been at an all-time low. You didn't say if the alternator was new or rebuilt, but rebuilt ones have a particularly high failure rate.
It's a rebuilt. I got aggravated, slammed the hood down and now everything is fine. Gotta be something loose.
I'd say you have a loose connection. When I had the problem with the corroded wire in mine it was intermittent as that connection was subject to vibration. Could be any of the connections to the alternator or a ground.