Help--Battery keeps going dead

[Doug27]

I have an all stock CJ7 , AMC 258 i6 / 4.2l . My battery has starting going completely dead. I've looked through the forums and was convinced that it was a bad voltage regulator. With no load, the battery showed 12.2 volts, with a load sometimes it would be 12.2, other times it would be 11.8.

I disconnected the alternator, re-connected the battery and got the same results (12.2 and 11.8). This suggests to me that the alternator/voltage regulator doesn't have anything to do with this issueWhile checking the reading one time, I noticed a flicker in the underhood light--which told me something turned on. I watched the meter and I can clearly see that something is cycling. I will start out at 12.2, then when something comes on, it drops to 11.8 for about 20 seconds. It then cycles off for about 30 seconds and then back on for 20. Any idea what would be cycling on and off? Does this appear to be a significant enough drain to kill the battery overnight? I appreciate any insight.

 

[Torxhead]

Interesting, You are going to have to keep searching. You might try disconnecting stuff like the computer, ignition control module, and distributor, before rechecking that voltage drop. 12.2 volts sounds a bit low for a good battery also. At least you have eliminated the alternator to begin with.

 

[harleydragon]

does the voltage jump up when running ?? if not then the alternator may still be the problem..if it does jump up I would suspect the battery

 

[tarry99]

I have an all stock CJ7 , AMC 258 i6 / 4.2l . My battery has starting going completely dead. I've looked through the forums and was convinced that it was a bad voltage regulator. With no load, the battery showed 12.2 volts, with a load sometimes it would be 12.2, other times it would be 11.8.

I disconnected the alternator, re-connected the battery and got the same results (12.2 and 11.8). This suggests to me that the alternator/voltage regulator doesn't have anything to do with this issueWhile checking the reading one time, I noticed a flicker in the underhood light--which told me something turned on. I watched the meter and I can clearly see that something is cycling. I will start out at 12.2, then when something comes on, it drops to 11.8 for about 20 seconds. It then cycles off for about 30 seconds and then back on for 20. Any idea what would be cycling on and off? Does this appear to be a significant enough drain to kill the battery overnight? I appreciate any insight.

Have you load tested the battery by itself?..........might be a bad cell in the Battery.......( very Common ) that is keeping the voltage down and not coming up to full charge.........That is the first place to Start!

 

[BlackOmega]

Interesting, You are going to have to keep searching. You might try disconnecting stuff like the computer, ignition control module, and distributor, before rechecking that voltage drop. 12.2 volts sounds a bit low for a good battery also. At least you have eliminated the alternator to begin with.

Exactly.
A good battery should be, at minimum, 12.5v. Even after a load test it should come right back to about the 12.5v mark. Typically, good batteries have ~12.7-13.0v.

Have you load tested the battery by itself?..........might be a bad cell in the Battery.......( very Common ) that is keeping the voltage down and not coming up to full charge.........That is the first place to Start!

Batteries have 6 2v cells. In series they combine and make the theoretical 12v. Batteries with bad cells typically only show ~10v.

Getting the battery tested is the first place to start. Usually you have to take it out, take it to a parts store or Sears, and have them load test it. The machine can detect a surface charge and will charge the battery if needed. Then it'll run a series of load tests on it that simulate starting an engine. This is usually the best way to test it since starting a car uses the most power and has the greatest amount of amperage.

Other indicators of a bad battery are leaks and a bulging case (the sides are rounded and not perfectly straight).

For what it's worth, all vehicles have some sort of parasitic draw. That draw keeps your clock going, radio presets and so on.

 

[TroyaCantrell]

Doug,

Did you test alternator output? With the engine running the output voltage must be above 13.5 VDC in order to charge the battery. Ideally closer to 14.4 VDC.

Also, testing battery voltage must be done with no load, disconnected, to get an accurate battery voltage.

What is completely dead, is that the 12.2? That should still crank the engine. If you are at 12.2 with the engine running then alternator or regulator would be my guess.

Always check your grounds throughly though as that could be your issue as well. That flicker in the hood light could also be a ground issue.

If you leave the battery even with 12.2 VDC come back the next day and it is under 12.0 you have a larger draw then normal, something wrong/ mis-wired and that is a different issue then the charging/ voltage issue.






Troy Cantrell
Sent from my iPhone using Tapatalk
Build thread - '66 CJ6 :
http://www.jeep-cj.com/forums/showthread.php?t=15075

 

[hdgapeach]

Simple (and CHEAP) method to check for parasitic draw down of the battery:
1. Everything turned off.
2. Remove the hood bulb to eliminate that electricity draw (and anything else known to be powered when Jeep is keyed off position).
3. Disconnect battery negative cable at the battery post.
4. Place circuit test light between the negative battery post and cable terminal end.

Any electric draw will cause the test light to burn. Make sure you have the test light attached securely at the cable end and battery post. Now you can move to the fuse panel and pull a fuse. If you don't notice at least a dimming of the test light, replace the fuse and pull another one. When you pull a fuse that is in a circuit that is causing the draw, the test light bulb will go out or at least dim. If it only dims, you may have more than one circuit drawing the battery down. Don't re-install that fuse. You want to keep all fuses out that cause the light to dim until you eventually get the test light to go out. Proceed through all the fuses one at a time. Any that cause the test light to go out have problems in their circuit. If you determine the faulty circuit (or circuits), that's when the real fun (work) begins - Got to trace the circuit(s) to dig up the cause (rubbed wire, bad sensor, accessory, etc.)

 

[BusaDave9]

I'm confused. What is the voltage with the engine off?
What is the voltage with the engine running at about 1500 RPM?

Bring the battery in to have it tested. A volt meter can't test to see if it's good. Any automotive store can test its load capabilities to see if it's really bad.

If it's good charge it up on the bench or with the leads disconnected. Connect it up and see if it goes dead overnight. Actually if it does go dead overnight you should be able to tell when you hook it up. It would spark as you put on the leads. If so then try removing fuses and disconnecting things to see if the sparks stop.

 

[BusaDave9]

3. Disconnect battery negative cable at the battery post.
4. Place circuit test light between the negative battery post and cable terminal end.

This test light will turn on with a good electrical system. The test light is a simple volt tester. To do this test correctly you need an Amp meter. That's a meter that measures electrical current. Most multimeters can measure current but you need to put the positive lead in a different location on the meter.

To read the current you must have the electricity go through the meter. To read voltage the meter checks 2 points and measures the difference in potential.
Almost no current goes through a meter that is set to read voltage.
There is almost no voltage across a meter that is set to read current.

EDIT: I'm not saying this can't be done as hdgapeach explained. I'm saying it can be very confusing to use a test light as an amp meter. The brighter the light the more current is flowing. ? ! ? If you want to do this test use an amp meter. A test light is a simple volt tester NOT a current meter.

 

[Doug27]

Thanks for all of the suggestions. With the engine idling and all hooked up, I am getting about 14.2V--that makes me fairly certain that it is not the alternator.

I'm certianly no electrical expert--didn't realize that 12.2V with no load doesn't necessarily indicate a good battery. I'll get it tested tomorrow--certainly easy enough to do.

Even if the battery is bad, is it normal to have something cycling on and off constantly? Is that drop from 12.2 to 11.8 when this cycle occurs enough to draw down a battery? If it does turn out to be a bad battery, I don't want to replace it if there is still another problem.

Even if it's not an issue, I'd like to know what that is--what cycles off and on like that continually?

Someone else had suggested potentially a faulty relay--any thoughts there?

 

[Doug27]

Sorry, forgot to answer one of the questions. Dead is zero. No lights, no click when you turn the key--nothing. A fully charged battery would get to this point in about 4 hours (I have the factory analog clock in the dash, so I know when it stopped). After I put the battery on the charger, no cables on it--that's when I was getting the 12.2.

Hooking up the cables (as long it was within the "off" of the cycling), it was still at about 12.2. The underhood light, clock (OEM), and stereo (aftermarket JVC), were not drawing enough power to appreciably change the 12.2.

 

[harleydragon]

aftermarket stereo is the only thing I can think of that would use any power with it turned off..yes,alternator sounds good

 

[tarry99]

Sorry, forgot to answer one of the questions. Dead is zero. No lights, no click when you turn the key--nothing. A fully charged battery would get to this point in about 4 hours (I have the factory analog clock in the dash, so I know when it stopped). After I put the battery on the charger, no cables on it--that's when I was getting the 12.2.

Hooking up the cables (as long it was within the "off" of the cycling), it was still at about 12.2. The underhood light, clock (OEM), and stereo (aftermarket JVC), were not drawing enough power to appreciably change the 12.2.

Like I mentioned..............First things First..... "Load Test the Battery" Once you know its good then move on through the check list!

 

[thescot]

Hung relay on the manifold heater? There should be no cycling of anything with the key off etc and whatever it is its more than a small light bulb. Even the stereo memory used a millivolts of power and not enough to kill the battery for weeks if not months.

 

[Barry2]

:dunno:It sounds like possibly you have a circuit breaker kicking in and out due to a short.

 

[Doug27]

Ok, going to start with having the battery tested today, but definitely agree that nothing should be cycling on and off.

If the battery checks out, I guess I can start with relays. Easy enough to unplug them one at a time to see if there is any change. Are all of the relays under the hood (I think I saw 3 or 4 hanging off of the wiring harness in various places)? What about circuit breakers? Where are those located?

 

[thescot]

I cannot recall there being any stock. I think it was mentioned but a good way to narrow down, if its not the battery is to pull one fuse at a time and see if the problem stops. I can say the last Chevy PU I had would start one time and the next had to be jumped. This could happen a few times in one day, it ended up being a bad cell. But again watching a voltage drop in cycles something else Id say.

 

[hdgapeach]

"The brighter the light the more current is flowing. ? ! ?"

Not what I was indicating at all. True as you state it, though. The point I was making was if you pull a fuse and the light goes out, you've found the circuit needing attention. If you pull a fuse and the light only dims, you may have more than one fused circuit involved (or breaker). It's rather obvious with a test light. No, it will not give the amp numbers as your method will. All I know is if you get the bulb to go out, there is no loss of amps.......or volts. Doesn't matter how bright or dim the light is when you start the search.

I stick by my "cheap / easy" method to test for parasitic drains, no matter how many amps the vehicle is losing. Most all older vehicles, especially the CJ generation, are pretty much off when everything is off. I know clocks, radios, and other electrical accessories draw amps continuously (unless the battery goes completely dead). From my experience, they draw so few amps I really don't ever remember them causing a 12 volt test light to indicate the draw unless they had a short causing an excessive amp draw (most of the newer vehicles also).

I'm not trying to stir you up BusaDave9. Just wanted to clarify what I obviously didn't state clearly in my first reply. I do more reading on here than replying for a reason. I've gained a lot from reading your posts and look forward to learning more from you in the future.

 

[Doug27]

Ok, latest update. Had the battery load tested today, it was fine. While I was as the store, I picked up a bulb as I had noticed that one of my underdash lights was out. I put the bulb in, turned the switch, and POP went the fuse. So now both lights, along with the underhood light are out. I pull the fuse and notice something is connected to that fuse with a fuse blade tap. Turns out to be the aftermarket stereo.

I haven't had time to investigate any further, but I think I'm making progress.

 

[BusaDave9]

I put the bulb in, turned the switch, and POP went the fuse. So now both lights, along with the underhood light are out. I pull the fuse and notice something is connected to that fuse with a fuse blade tap. Turns out to be the aftermarket stereo.

Okay, you found a short. Leave the fuse out and the stereo disconnected from power. Does the battery now stay charged? Don't rewire anything until we are sure we have the short verified. If the battery stays charged with the stereo disconnected then wire it back up correctly.