QuestionQUESTION: Hi--
I'm hoping you can help me.
I have a 66 Impala. This problem has been happening for years. Here is a typical occurence. I have a battery freshly and fully charged. I hook it up and the car starts fine. If I drive it a short distance, I can turn it off and it will start again. If I drive it 15-20 miles, stop it, and go in for lunch, The battery is completely dead. After a jump start, I can take off again. The last time this happened, the nice guy who gave me a jump start said that I have the "old type of generator". He tapped on a separate piece and said "the inside of these voltage regulators sometimes stick." He said I can check this by removing the two wires that go into the back of the generator and then see if it "starts right up". Can you please explain this to me? Have you heard of this voltage regulator problem before? What would you suggest? Any help would be greatly appreciated.
ANSWER: The last year for generators for full size Chevrolets was 1962, so your car should have an alternator. If it has a generator, someone has switched it. To tell the difference, a generator is a large black cylindrical device, about 10 inches long and about 6 inches in diameter - similar in appearance to your AC compressor. An alternator is much shorter and fatter around, and is an aluminum casting (gray in color).
From what you say, something is discharging your battery very rapidly - and whatever that is has to be getting VERY HOT! - so don't leave the car with the battery connected until you get it fixed - in fact I'm amazed you haven't had a fire because of this problem.
Yes, it is possible that IF you have a generator in your car, a sticking regulator can cause this symptom. I have seen two cars burn up due to this problem - so don't do anything else with the car without disconnecting the battery every time you turn it off.
If you have an alternator, the discharge problem can be in the alternator due to a bad diode - in which case IT will get VERY HOT, or the regulator can be sticking too - so again, disconnect the battery every time you turn it off. Take the car to an auto-electric shop and have them track it down with meters to see where the discharge is taking place. In the meantime, you can drive the car, but disconnect the battery every time you turn it off, even for a few minutes.
I can't diagnose it further without testing the car myself - and if you do not have electrical testing equipment, you will have to take it to a professional.
Sorry I can't be more help.
Dick
---------- FOLLOW-UP ----------
QUESTION: I'm pretty sure I have an alternator. It is short and gray colored. I was just quoting the guy who helped me. The regulator is separate from the generator, correct? It seems to be mounted on metal, I assume this is so it will be properly grounded. You are now the second guy to mention a "sticking" regulator. What exactly does this mean? Thanks for your timely response and your expertise.
AnswerYes, well, I don't know what the guy was referring to when he said you have the old style generator.
Anyway, yes, for your year, the regulator is a separate device (a few years later they woke up and included them in the alternator - a much better design because it eliminated the relay contacts).
Your regulator contains a relay which connects the alternator output wire to the battery when the regulator decides that the battery needs some charging current. It is supposed to automatically disconnect that wire when the engine is turned off, and the way it does that is by releasing the relay contacts. If the relay sticks shut, due to wear or corrosion on the contacts, or due to a wiring error in the car, it leaves the battery connected to the alternator even when the engine is off - thus providing a path for the battery to discharge through the alternator. The diodes in the alternator should prevent serious discharge even should the contacts stick - so I think in your case you may have two problems - one or more bad diodes in the alternator, and a sticking regulator. Since you might spend a lot of money just replacing parts without proper diagnosis, I think you should take it to a shop which is equipped to see what is going on before you throw money away.
Depending on where you live, you may find that your local auto parts chain store has a free diagnostic service for charging problems - out here in CA, AutoZone provides this service. If you have a similar service in your area, take the car there and ask them to check it out. I don't have a lot of faith in the training the counter folks at these stores receive, but maybe they will sort it out for you. Don't forget to lift off one of the battery cables when you park the car!
Dick
