Stop The Bleeding ?

After sitting for 3 weeks, my battery died, or so I thought. The digital charger showed "fault".
So I go buy a bigger and better battery. After sitting for a couple of weeks, it was dead also.
Digital charger showed "fault" again..
I jump started the jeep and let it run for 20-30 minutes, killed it and it started right up. Then I put the same charger back on and let charge over night until it was fully charged. Installed a master switch at that
point, and have had no more problem.
The question is: what is the best way to chase down the "bleed" in the wiring? I have an alternator
on the engine, no voltage regulator. Have not seen any indication of any lights trying to shine after ignition switch is off, and everything else seems to work normal..

 

We need year, model, equipment - this should be in every post. We also need the type of alternator.

Do you have a multimeter? Measure the current from the disconnected negative cable to the battery. Start on the highest current setting, since a current measurement is essentially a short through the meter.

 

Obviously different situation, but I had a 1993 f150 that would kill the battery due to a bad alternator. Simple swap and was good to go again.

 

I too have had an alternator that drained the battery - cured by replacing the alternator. However, I strongly advise that the OP start by measuring, rather than randomly throwing parts at the problem. As Hamlet would say, get thee to a multimeter. A test light might work too, but is vastly inferior for this problem, IMO.

 

I differ with Tim on the use of a test light to diagnose this issue. Disconnect the negative cable at the battery, put the test light in series between the battery negative terminal and cable. With a draw on the battery with enough amperage to light the tester is enough to drain the battery. Disconnect components until the test light goes out. Problem found.

 

I've had a similar problem with my YJ for years. Replacing the alternator did not help.

One problem in diagnosing is that there are legitimate "ghost" loads such as the dash clock.

Another difficulty is that it is difficult to locate the right wire or otherwise impossible to "just disconnect" many components.

 

I always start by pulling fuses on vehicles that have them.

 

A dash clock or LED indicator lights will be very tiny current drains, which you could rule out with a multimeter amps measurement. Plus, methinks these are way more likely present in modern cars, where tiny continual loads maintain the computer memory and such. My VW, for example, has flashing LEDs by the door lock buttons that signal the alarm is set. I believe this is more of a theft deterrent than of practical value, but they are there. And they shut off automatically after about a week of idleness.

Most of you should be able to figure out where such parasitic loads come from.

You can get an idea of whether the leakage load you measure is significant by comparing it with the amp-hour rating of the battery. A drain of 20 mA will drain a typical 50 amp-hour battery in (50 amp hours / 0.020 amps) which equals about 14 weeks. Likely drained half-way is enough to keep you from starting a long-idle engine, so more than a month. This also assumes a battery in perfect condition and fully charged.

Really, when you measure the amp drain as above, you should get zero unless these is something wrong. BTDT. Don't accept some minor drain, if it's supposed to be zero.

Regarding a test light versus a multimeter, I did not respond earlier because Oldoriginal86 is right - you can use a test light for this, and you'll likely be able to figure it out. However, it is also true that a multimeter will tell you more than a test light. How much parasitic load is needed to see it in a test light? I don't know. Better multimeters have a microamps scale, and even a cheap meter should be able to measure well less than 100 microamps.

Despite its size, a multimeter is a powerful instrument, and you increase your personal diagnostic power by many times when you use and understand it. A test light is good too, but to my mind, it's a workaround that requires more electrical understanding than a meter.

You also need to read the wiring diagram. Pulling fuses is fine, but that's a strategy of "divide and conquer." When you don't have a lot of fuses or a central fuse panel, you must look at the diagram and figure out how to isolate parts of the harness. Same strategy.

 

Due to the ghost load being so slight, and being partly legit, I would have to wait 2 days each time to see if the battery still died - and repeated cycles like that damage a battery. The wiring diagram is complex, and each fuse serves multiple items.

Admittedly this would be a lot easier on an earlier vehicle.

 

This would be done with the test light between the the battery and cable, results are instant. Some parasitic load will be present in any vehicle. An alternator when in perfect operating condition will have milliamps of draw however it won’t kill the battery over a few days. It’s the large amp pulling shorts that will light a test light that we are worried about here.

 

Then I'm still baffled because with a meter, the draw is barely registering. But it definitely kills the battery.

 

question, does it light a test light? 6 or 12v respectively

 

My opinion - "Some parasitic load will be present in any vehicle " - I don't believe it. Batteries don't maintain a charge on their own indefinitely, but that's not the fault of the wiring. Batteries self-discharge over time without help from connections to car wiring. IMO any car that's not driven every few days should be on a battery maintenance charger.

To Pete, I would disconnect the battery cables, leave the battery in the Jeep and see if it runs down.

 

This. Easiest test to make and best place to start. Make sure the battery is level if lead acid (park jeep not on steep side hill).

 

Not the battery.. I've got a main cutoff switch, and for several years now I use that. The battery is fine when isolated.

BTW - When I was a kid I had a '51 Pontiac I only used in the summer. The 6 volt battery would start it after 9 or 10 months idle. (!)

I feel like I shouldn't be hi-jacking this thread - a YJ is quite a different animal than the OP asked about.

 

I,m back finally.. The jeep in question is a 64 cj5, f134, delco alternator with two wires, electric fuel pump and one electric wiper.. Everything else
is stock. This problem just started two months ago. Worked fine for 9 years, just started. I checked with the neg. cable off with a "volt meter" from the loose cable to neg. post on battery and got 12.5v.. {got to dig out the multimeter} The voltmeter on the dash is wired behind the ign. switch so when the switch is off, so is the voltmeter.
The only other thing that has been done, I installed electronic ignition maybe 18 months ago. I appreciate the comments and suggestions from you folks, as you never know who will ring the bell..

 

Is the electronic ignition on a relay that is switched with the ignition, or connected directly to the battery? What brand/type electronic ignition?

The voltmeter won't register a voltage unless there is some leakage through the wiring. However, the input impedance of your voltmeter is likely so high that even the tiniest leakage will give a reading. The amps setting in a multimeter will tell you more.

 

It,s a petronix and is wired through the key switch and stand alone switch.