Auto Electronics: voltage regulator, 2001 ford windstar, ford windstar

Question
I have a 2001 Ford Windstar. Everything works fine while it's running, but the battery dies overnight. I'm guessing the voltage regulator. What do you think? Can this be replaced with out changing the alternator?

Answer
David, three things could be causing this problem, the battery, the charging system, and a parasitic drain on the system. The problem should be diagnosed in that order. First the battery, make sure it is fully charged, then have it load tested to ensure it is capable of retaining a charge. Next the charging system should be capable of charging the battery and supplying excess system needs. Finally a parasitic drain on the battery. You are suggesting this with your guess of a bad voltage regulator. While it is possible that the voltage regulator could cause this, it is very unlikely. A shorted diode in the alternator could cause this as well, but the most likely suspect would be a module in the system that will not go into sleep mode for various reasons. Diagnosing these type problems are difficult and time consuming, requiring special tools and experience. I would suggest you find a good mechanic who has experience tracing down these type problems. Good luck. Don.