I woke up in the morning. Car started right up. Drove to work.

Went to the store at lunch. Car started right up.

Went home. Car started right up.

Went inside and had lunch. Half an hour later I get into my car. No sound. No lights. Nothing when I turn the key.

So I take my girlfriend's car back to work, come home and go to bed.

The next morning I jump the car using her battery.

I notice that the dome light is on. I check to see if any of the doors are slightly ajar. None of them are. I forgot to check and see if the headlight switch was turned to the left, turning on the dome light. Dumb. But I hadn't gotten much sleep. So I just pulled out the bulb.

I drive to Napa. 50 minute drive. When I get there I have them test the battery. It reads 12.8 amps. Guy says the battery has about 1/3 of its life remaining.

The car has been sitting for maybe ten minutes. It starts right up.

I go to the hardware store to buy Dan's recommended 303 to get my vinyl protected and looking great.

10 minutes later, car starts right up.

4 hours later, car is dead. No lights no sound when I turn the key. So somebody gives me a jump.

I know I need to read my FSM on electrical systems but I have somewhere to be tomorrow. If I jump start my car, drive for an hour so the battery is nice and charged, then disconnect my negative battery cable will that keep whatever is draining my battery from draining it so I can get home?

Alternator gauge was one tick to the right when I was driving home this morning after the car not being started for 15 hours but its now dead center.

Thank you

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God took you away, then brought you back to me.

Sounds like a bad cell............

Let it sit, then measure the voltage.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Have you checked your battery connections to make sure they are clean and tight?

A lot of things can draw power and run the battery flat - if you disconnect the battery and it still goes flat, you've got an internal battery problem. If it doesn't, the drain is external. You can put a test light in series with the battery (between the - post and the - clamp) and if it lights up, it's trying to draw power.

The alternator diodes can start leaking and cause the drain even if you pull all the fuses - if it stops, I'd check the radio memory next.

"The battery read 12.8 amps and the guy says it has about 1/3 life left" makes no sense at all. It probably read 12.8 volts, but there's no test the counterman could've done to come up with a sound basis for saying long the battery has left, in relative or absolute terms. Perhaps he was making a guess based on the production date of the battery, which is often revealed by its label. How old is this battery?

A dead cell in the battery will cause slow engine cranking and the ammeter to ride way over to the right much of the time; doesn't sound like your symptom, but it's easy enough to test: with the engine off, turn on the headlights for two full minutes, then turn them off and measure the voltage across the battery. If it is closer to 10.6 than to 12.7, you've got a dead cell.

It's possible the battery has a faulty internal connector making intermittent contact. It's also possible the battery has a faulty external connector (i.e., a bad + or - battery cable) making intermittent contact, or the battery-to-cable junction may be dirty. Any of these can easily mimic a faulty battery, and can really throw you off the trail since a jump start seems to "fix" the problem (actually by dint of jostling the connections and/or cables).

Even if you have an electronic stereo, it is not a likely cause of your battery drain; the memory in such radios takes a tiny amount of current; it could not even begin to drain a healthy battery flat over the course of four hours.

A larger-than-tiny (but still small) drain on a battery, such as a dome light left on, will do more damage to a battery than a large drain such as the headlamps left on. If the dome light was in fact on long enough to flatten the battery, and the battery was nearing the end of its life anyhow, it could have been enough to push the battery into the dead zone of intermittent reliability.

Since the dome light is a potential suspect, check it first: replace the bulb, turn it off via the headlight knob, close all the doors, and check if its lit. If it is, adjust the door switches by grasping their plungers with a small pair of pliers and giving a firm but not hamfisted jerk outward. Then close the door, and the switch will be adjusted correctly. If that still doesn't turn off the dome light, find and fix the circuit problem.

Check for spurious current draw: turn everything off, close the doors, and remove the negative cable from the battery. Put the + lead of a voltmeter on the battery negative cable clamp, and the - lead on the battery negative terminal post. If you have an electronic stereo, you may see a voltage reading. Otherwise, there should be zero voltage shown. If you have an electronic stereo, remove its fuse and repeat the test. Keep removing fuses one at a time until you find the one that stops the voltage, then focus in on that circuit to find the draw. Trunk lights and such are common culprits, easy to miss because they're out of sight.

But I suspect you don't have current flattening your battery; I think you've got a faulty battery cable and/or battery.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Terminals have been cleaned.

Negative battery cable has been replaced. (Napa gave me the wrong positive cable so I'll have to go back for that one.)

Switches for dome light on doors have been tested and they move easily in their housing. A light pull with the pliers and a shot of PB Blaster was applied to each just in case.

Dome light was staying on regardless of switch (headlight) position before these repairs, it now functions correctly. I also pulled the dome light down to see the condition of the insulation on the wires up inside the headliner and while old, the insulation had not cracked or begun to peel off.

I am leaving the cable off of the battery tonight to see if the battery is indeed faulty. If she starts up in the morning diagnosis will continue from there.

Thanks for all the help.
Your getting me to work in the morning is good for the economy!
M

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God took you away, then brought you back to me.

And after sitting all night with the negative cable disconnected she starts right up. So it's time to get a voltmeter and find the source of the drain.

Thanks again
M

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God took you away, then brought you back to me.

The FSM's usually say a few mA is an acceptable leakage in the alt diodes, so a 2Mohm DMM (quite typical) can read 12V when placed between in series with the battery even if the drain is small. Radio memories usually take a few mA or less. If a 12V test light does not light up, you can safely put the meter into current mode and directly measure the current; but don't do that before you've established that the current is small or you can damage the meter (don't count on the fuse to blow fast enough to protect the meter).

I have heard a complaint from a colleage that his early aftermarket electronics took ~100mA of current for its memory, but that was years ago.