My damn battery keeps dying on me. Replaced it once, believed it was a simple dead battery, two days later that one went out on me, had it tested and it was shown to be a bad battery, so I changed out the alternator, got yet another battery, and low and behold this one has gone out again. I have no idea whats going on with this any suggestions please let me know.
This is on my 1980 L-48.

|UPDATED|1/6/2004 11:34:46 AM (AZT)|/UPDATED|

I had a similar problem several months ago. It turned out (in my case), the delay timer for the courtesy lights had gone bad and was sometimes working normally, sometimes not turning the courtesy lights off at all after the 20-40 second delay time, and was even turning the lights on at random and staying on.

One thing you can do is put a volt meter on your battery when fully charged, and pull one fuse at a time from the fuse box. See if you have a noticeable increase when a fuse is pulled. If so, something on that circuit is on and draining power. From there it's a matter of isolating the individual problem and correcting it. Remember, if you do this with the door or hood open, you'll have courtesy lights on, so make sure those lights are off when testing.

Actually an amp meter works much better and is more accurate. Anything over .5 amp will kill the battery when the car sits. Ideally it should be less tha .3 amp. The reason the volt meter is not reliable is the electronics in the car, any timers, radio memory, etc. that use any power at all will cause the volt meter to read 12 volts, even with less than .1 amp draw. If your car does not have any of these devices the volt meter will work fine.

Ken Styer

I have the same problem with my '74. Turns out there is a partial short in the interior lite circuit which is on the same fuse as the clock and cigarette lighter.The amp meter is the best way to find it... just keep removing things 'till you find the faulty circuit.

I stand corrected. I've used a voltmeter before, but understand now why the amp meter is a better way. Thanks all for the hint.

Not sure where you all have gotten your numbers but a parasitic drain of more than .075 amps is a problem. If the battery runs down in 2 days while sitting, then it would indicate you have a darin of 2 amp. About 25 times higher than what should be considered a OK.

The best tool for the job is an amp meter. Volt meter won't get it done. If you don't have an amp meter or don't know how to use one ---Here is a way to find your problem with almost no cost/tools.

Connect a 12-volt bulb in series between the negative battery cable terminal clamp and the negative battery terminal. (put it in between the battery and the cable If the bulb continues to glow brightly, then start removing fuses or connections to the positive battery post one-at-a-time until the offending electrical component is identified by the bulb dimming. Note:engine NOT running, under hood light disconnected, all accessories switched off, and the vehicle doors closed.

.075 amp is specs for some cars. As you say, it takes a lot more than that to kill the battery. The numbers I gave are generic from battery mfgs. for what will make any battery go dead. The smaller spec quoted is for the auto mfg. spec for a specfic car. Some are higher. As any car ages the amp draw raises due to component wear and corrosion causing drain. You can exceed the factory spec and not have a dead battery.
The light bulb test may work, but many times not for a couple of reasons. First, what 12 volt bulb are you using. Ohm's Law needed here.
If the bulb requires 1 amp to light and the draw is .5, the battery will go dead, but the light won't light. If the bulb requires .3 amp to light that would show a threshold level and would work, but that depends on what the draw is. Most of the time it's a resistance. When you put the bulb in series with the resistance, you increase total resistance. So using the example of a glove box light using .3 amp. The test bulb may also use .3 amp. This splits the resistance of the circuit and that splits the voltage of the circuit. Now each bulb will only have 6 volts, not 12 volts, and neither light will come on, but the battery will go dead.
Not saying the bulb is not a good test, it is, it's just is not going to catch several things. If the bulb comes on and you disconnect things until it goes out, you have found the problem. But you could also have no light and not find the problem. If your test bulb only uses .1 amp your chances of finding the problem go up quite a lot, so use a small bulb. LED's won't work for this test.
If you don't have an amp gauge, use the bulb and it may work for you, but the amp gauge is a sure test, and much more accurate. Hope this helps.

Ken Styer

Could be so many things.
I had the same problem recently.
Turned out to be the lamp switch in the vanity mirror behind the passenger sun visor. Little plastic piece of s&^$.
Drove me nuts for a few days.

Good luck........

i had the right tail-lamp stay on in a 66 plymouth i once had. drove me nuts. It was a shorted wire for the turn signal inside of the steering column. don't know why only the tail lamp lit and not the tail and the front lamp? hope yours is easier than mine to find.

The worst one I ever ran into was a VW Rabbit. It only went dead sitting in front of his house. In the drive or anywhere else it was fine. Parked out front, the right rear wheel hit the curb, flexed the body and the hatch would move just enough to turn on the rear interior light. Drove me nuts. I found it by accident by pushing the car forward in the service bay to work on something else. When the right rear tire hit the rack, the amp gauge shot up. Readjusting the hatch and latch fixed it. I know it's not a C3, but I thought you may find it interesting.

Ken Styer