QuestionMy restored 1964 1/2 Mustang with a generator and 260 engine has suddenly been discharging the battery in 24 hours. I replaced the battery, no help. There are no lights on or fan motor running. I have not done any electrical repairs that would be the issue. Could it be the voltage regulator? I do not have diagonistic equipment, so how can I find the problem?
Thanks so much for your help.
Dave
AnswerThere are literally hundreds of possibilties here, but one of them is indeed the charging system. If the discharge is through the charging system, it would be caused by the regulator contacts sticking, and the easiest symptom to find is that the generator will be hot long after the engine is shut off - in fact there have been serious fires caused by this problem.
I assume you have been disconnecting a battery cable each time you park the car. If you have not been doing this, I strongly advise you to do that. Leave the clamp bolt loose on one of the battery terminals so you can slip the cable end up off the battery post each time you turn the car off; failing to do that can cause the complete loss of the car due to fire.
In order to diagnose the problem, next time you connect the battery, tap the cable end on the battery post lightly while you watch for a spark to occur at the point of first contact. If there is a spark, check to make sure nothing in the car is turned on, and the doors are closed. If you have an operating original type clock in the car, there will be a spark as the clock winds, but that will only occur at the first contact, so repeat the momentary contact a second time after the clock winds, to see if a repeated spark occurs. If it does, the problem is not intermittent. Very likely, it is something else in the car that is running down the battery, not the charging system. We'll come back to this thread later.
If the spark does not occur (or if you have the orignal clock which works, so that the spark only occurs the first time), the problem apparently goes away when you disconnect the battery. This is a common situation with a sticking regulator, because the sticking relay contact in the regulator releases when the battery is disconnected. Start the engine, and let it run for a few minutes to charge the battery a bit. Then, with the engine running, lift the battery cable off the battery post (it won't electrocute you - in fact you won't even feel it, it's only 12 volts!) to see if the engine stalls immediately. If it does, your charging system is not operating correctly, and you will need to take the car to an auto-parts store which offers free diagnosis of charging problems. Auto-Zone offers that service out here in California - as do others elsewhere in the country.
If the engine keeps running with the battery disconnected, you know the charging system is providing the current to run the engine, so it is proven to be operating, at least fairly well. This does not eliminate the regulator as the culprit in your problem, however. Continuing in this thread, reconnnect the battery cable and turn off the engine. Now, with your ear near the regulator, lift off the battery cable again and see if you can hear a "click" inside the regulator as you break the contact with the battery the first time. If you hear this click, the regulator is sticking, and needs to be replaced. You can continue to operate the car, but you must lift off the battery cable each time you turn off the car to prevent a fire from an overheated generator.
Now back to the first discussion: If the spark always occurs, even after the clock has wound, the problem is going to be a little more difficult to find.
Since the battery discharges with the key off, we know the problem is in one of the circuits that are "hot" with the key off. This eliminates many possible causes, but leaves us with a few:
1. Interior "convenience" options - like courtesy lights, clock, glove box and trunk lights, cigarette lighters etc. I doubt your car has power seats or windows, but if it does, that is another possibility if they operate with the key off.
Also, if the car has any aftermarket accessories, like a modern stereo, those are very likely candidates - so disconnect them from the 12 volt system to see if the symptom clears. Most modern stereos have 3 or even 4 different 12 volt inputs - be sure to disconnect all of them. (Why, you ask? One for the memory (remembers your push button settings and the time), one for the power antenna switch (retracts the antenna automatically when the key is turned off), one for the dial lights (go up and down with the dash dimmer control) and one for the main function (the radio tuner/amplifier). The stereo probably has one or two multi-wire connectors, unplug ALL of them.
2. Other items that work with the key off, such as exterior lights (don't forget the brake lights) and the horn. As a shot in the dark, I have to ask you if your horn works properly. If your horn is inoperable, your horn relay may be stuck on, either due to a ground in the steering column or some wiring problem. To eliminate this as a possibility, disconnect the wire from the "B" terminal on your horn relay. The charging system is supposed to be disconnected automatically when you turn the key off, but if the relay contact is sticking "on" as discussed above, it has to be considered in this category also.
The only way to track it down from here is to disconnect or remove the fuse from each of these items, one by one, rechecking after each one to see if the spark stops happening when you tap the cable. Since you have a fairly large discharge (because it dumps the battery in 24 hours), I think you can find it this way.
If the spark is too weak to see, or you cannot detect it, you will have to get a multi-meter to assist you. If you are going to be maintaining this or any other car, you should really have one - I advise you to go to the local Radio Shack outlet and buy one with an analog dial (not the more modern "digital") and with a current range of at least 30 Amperes. Set the meter on the highest current range, then connect it with the red (+) test lead on the battery ground cable end, and the black (-) test lead on the negative battery cable post. It will show you how much current is draining. You can use sucessivly more sensitive scales on the meter until you get a significant reading, then start disconnecting things and pulling fuses. To check whether the voltage regulator is the culprit, unplug the multi-wire connector from the regulator - if that stops the current drain, you've found it!
This is enough for now. Please let me know if this helps, and if you need more, just ask.
Dick
