2001 Cavalier Battery Drain Problem - HELP

Hello everyone! I have been reading these threads for a long time, but this is my first post. I am at wits end!

My 2001 Cavalier has been having a battery drain problem for almost 2 years now. The battery dies overnight, especially when the weather drops below 30F. It doesn't always do this, particularly in recent weeks, when it may die within 4 hours or be just fine after 36 (regardless of the weather). We have replaced the battery twice (once was a free switch via warranty), and taken it to the dealership for testing; they told us they "could not duplicate the problem, and that battery draw tests were within spec." Autozone has tested the battery and alternator, both of which were fine. Recently, I have tried cleaning the positive and negative terminals of the battery, and also replaced the blower motor resistor (based on some posts I read here). For 2 days, the car started perfectly, and I thought I had finally solved the problem! Then, for a week, it was dead every other day or randomly while it sat in the parking lot at work. It can sit for 14 hours and be just fine, then sit for 8 hours (after a 30 mile drive) and be dead.

We found, for a long time, that pulling the fuse for the instrument cluster while the vehicle sat actually prevented the problem. Now, however, that makes no difference (as if the problem has gotten worse?). I have an aftermarket stereo that uses the windshield wiper fuse as a switched 12v power source - this was installed for 2 years before the problems began, but doesn't seem related (I tried unplugging it completely for 2 weeks without effect). Otherwise, the car is stock.

If anyone has any ideas, I would greatly appreciate it! I have done everything I can think of, and nothing has worked yet.

First of all, if you're worried about your battery dying while you're away from your car you can always remove the ground cable from the battery when you're done driving it. This will keep your battery from draining.

It sounds like you may have a short in your circuitry. Here's one way to test for this:

1.) Turn your car off.
2.) Pull a fuse from your fuse box.
3.) Connect a test light or voltmeter to the terminals where the fuse used to be.
There should not be any voltage across those terminals, with the exceptions of the cigarette lighter/horn, and anything else that is supposed to stay on when the car is off. If you get a voltage across the terminals, you've found a short that may be causing your battery to drain.
4.) Repeat with other fuses until short is found.

Note: You'll need to do this when your battery is not already drained.

Here is an update after some tests I did today (thanks 96DropTopFire). I drove the car today for roughly an hour to charge the battery (after jumping it this morning). I then took my trusty multimeter and checked the amperage being drawn off the battery when the car was off. After the initial computer startup, the drain dropped to 0.08 amps (80 milliamps I think). I have read in other threads that the drain is supposed to be anywhere from 75-125 milliamps, please correct me if this is wrong!

The other thing I noted was that the drain dropped to pretty much 0 when I pulled the fuse for the instrument cluster. Also, the voltage across the battery was 12.26 (after an hour of highway driving). The instruction manual for the multimeter indicated that this represents a battery that is only 10-25% charged! I have left the battery cable off as 96DropTopFire suggested - I guess if the battery dies anyway, it really is the battery!!

Thanks everyone!

With the car off, the battery reconnected, and the fuse for the instrument cluster pulled, put your multimeter leads into the terminals for the instrument cluster fuse. If you read a voltage, you likely have a battery-draining short.

Also, when was the last time you had your battery tested? I know you've replaced it recently, but if you're constantly draining it to the point where you have to jump it, the strain may have taken a toll on the health of the battery.

When you say the battery goes totally dead do you mean it won't even turn the starter or anything, and have you ever actually checked the battery voltage at the terminals when it's dead? It could be possible that your battery isn't being drained and getting dead at all. You could have a battery cable connection that is intermitently going open. When you said you drove it for awhile and battery voltage was only 12.26v (not running right?)that sounds like a battery that's not even connected to the charging system/electrical system.
Next time your battery goes dead, check the battery voltage at the battery with a voltmeter. If you have 12v at the battery but no voltage to the car, that would tell you there's a bad connection somewhere in one of the battery cables.

I guess I didn't specify, when I say the battery is dead, usually it is just low (low enough that the car won't turn over, but the starter solenoid clicks). All the lights come on, and the radio will go, its just not enough juice to turn the engine over. Either way, I am definitely going to check the battery voltage the next time it is low! I also plan on getting the battery fully charged and doing a load test at Autozone to see if it is permanently damaged from all the jumping (I didn't realize that was a possibility until today). It hasn't been tested in about a year, but it went all summer last year without a problem!

Use a battery charger to charge the battery! The alternator is not designed to charge a dead battery. You'll burn up the alternator if you do that too much, not to mention that the battery should not be charged at the amperage that a good alternator will put out. For a battery the size of yours, I wouldn't go higher than 20A, and the lower you charge it, the longer the battery will last. Technically, .05A is the maximum parasitic draw. .25A won't kill a good battery even if left to sit for a few days. If the battery does go dead while disconnected, check for case draw. As the battery is charged, a very small amount of electrolyte evaporates. Some of it condenses over the battery and fprms a conductive layer. With your voltmeter, put one probe on a battery terminal and the other vary close to the other terminal (but only touching the plastic case). If you read anything other than the floating mV that a lot of meters show, clean the case with baking soda and water. You should also check the electrolyte level in the battery periodically, but most people either don't know that or just don't do it. I once added 20 oz of water to a battery (78 series, only slightly larger than your 75 series).

I guess I didn't specify, when I say the battery is dead, usually it is just low (low enough that the car won't turn over, but the starter solenoid clicks). All the lights come on, and the radio will go, its just not enough juice to turn the engine over. Either way, I am definitely going to check the battery voltage the next time it is low! I also plan on getting the battery fully charged and doing a load test at Autozone to see if it is permanently damaged from all the jumping (I didn't realize that was a possibility until today). It hasn't been tested in about a year, but it went all summer last year without a problem!

Well yeah those details change everything. You still need to know what your battery voltage is at the battery. I take it the battery/alternator light doesn't come on right? This car has battery run down protection so it's less likely you have a parasitic drain causing this problem. It could be a lot of things, too small/defective battery or discharging to the case along the lines of what J-ri said, corrode battery terminals or bad connection, a starter that pulls too much current. Doesn't sound like this car is being properly diagnosed by whoever looked at it. Have Autozone or whoever load test the battery, starter and alternator. You live in the same city as me. I'm not looking for a repair job or anything though :lol2:.

A quick update. I tested the voltage this morning after letting the battery sit all night unplugged from the car (and in the 30's last night), and the voltage had dropped to 12.17 (down from 12.26 yesterday). I don't know if a drop of .09 volts is something to be concerned about or not! As for the battery drawing volts off the case (J-Ri, thanks), I checked that and showed .01 volts on the meter (with a solid .00 showing when the probes aren't touching anything. Again, is that enough to be concerned by? Finally, the battery is sealed, so I don't really know how I could add water even if I wanted to.

Another odd thing I noted this morning - yesterday, the draw on the battery was .08 amps, this morning it was .09. I have no idea if this is relavant or not, but thought I would mention it. I will have it charged up and tested ASAP, and post the results when its done!

A quick update. I tested the voltage this morning after letting the battery sit all night unplugged from the car (and in the 30's last night), and the voltage had dropped to 12.17 (down from 12.26 yesterday). I don't know if a drop of .09 volts is something to be concerned about or not! As for the battery drawing volts off the case (J-Ri, thanks), I checked that and showed .01 volts on the meter (with a solid .00 showing when the probes aren't touching anything. Again, is that enough to be concerned by? Finally, the battery is sealed, so I don't really know how I could add water even if I wanted to.

Another odd thing I noted this morning - yesterday, the draw on the battery was .08 amps, this morning it was .09. I have no idea if this is relavant or not, but thought I would mention it. I will have it charged up and tested ASAP, and post the results when its done!

Well your battery is not showing discharge to the case or a parasitic drain, but it is way undercharged. Does your alternator/battery light stay on? You could check the batttery voltage while it's hooked up and running and see if it gets up to around 13.6 volts. You should just get the battery/alternator/starter tested. Provided your battery connections are sound it's sounding like a bad battery or maybe a starter that pulls too much current.

Did you ever check the electrolyte level? It should be to the bottom of the 3/4 way around "tubes" that lead from the top of the case. It's normal for it to drop a bit, but you should never let it get below the top of the plates. Also check the electrolyte with a battery hydrometer to make sure you don't have a weak cell. What brand of battery is this? Some of the cheap ones sold by a large nation-wide chain will never start the car past a year or so, regardless of the free replacement warranty. A lot of other cheap batteries are bad too, but those are by far the worst. Get an Interstate/Duralast/champion. They are all made by the same manufacturer, although Interstates seem to be the best of them. Possibly because that's what we sell, and our customers almost always come back to us for everything, including oil changes. With the oil change we check/fill the electrolyte, so most of the interstates I see last longer. I have a Duralast in my truck that I bought in '02. I always keep the level full, and it still passes the load test 350A for 15 seconds and it doesn't drop below 10V.

That small of a voltage drop overnight is normal, but would be less on a fully charged battery. .01A rise may just in the meter, although if a device is using "X" watts, when the voltage drops, amperage has to increase to keep the same power. last night you were using .9808W (12.26v*.08A=.9808W), and this morning you were using 1.0953W. I would attribute that to inaccuracy in the meter .1145W is very little.

All right, an update to this problem (definitely not a solution, just more information...). I charged the battery today with a 2 amp charger for about 6 hours.. prior to the charge, the voltage was 12.28, after the charge it was 12.53 volts. I then took it straight to autozone to have it tested. The test ran for a little while, then had an error message ("Charge and retest"). I have been leaving the battery unplugged from the car every time it sits for longer than an hour, and it hasn't died since Thursday! I intend to take the battery back to autozone to have them charge it, then run the test again.

On that note, does anyone think this could be a bad diode on the alternator? Would I have seen other signs (such as a larger drain than .08 when the multimeter is set to 10A, or the car shutting down after driving for a while, or a light on my dash) beyond the discharging battery? If not, how can I test this?

You charged the battery for 12 amp-hours, I haven't seen a battery rated in amp-hours in a long time, but most in cars are in the 60 amp-hour range. Charge it longer. 12.53V is the surface charge. After charging it, remove the surface charge by turning the headlights on for 10 seconds. That will leave you with an accurate voltage, but even 12.53v is not fully charged (should be 12.6)... a surface charged battery will usually be over 13v.

If pulling the fuses didn't point to the draw, you should also disconnect any non-fused things, usually just the starter and alternator. A bad diode probably wouldn't cause any noticeable problems, several could, but wouldn't cause a draw. The voltage regulator can draw a bit if there's a partial short to ground... disconnect both alternator connectors (B+ and plastic multi-wire) and see if the draw goes away or down. I still think the problem is in the battery because .08A is barely over the limit. if you let the car sit for 100 hours (just over 4 days) the total drain on the battery would be 8 amp-hours. That would be about the equivalent of leaving the headlights on for about 30-45 minutes (which any good battery could take)

Ok, took the battery to autozone to charge and test it. Surprise, surprise, it failed! So, bought a new battery, and will now monitor it to see if the drain is still happening or if it was just the battery.

Just for fun, I checked the AC voltage at the battery while the car was running - 32.8 volts AC on the display with the meter set to 200 VAC! Something about this doesn't seem right, and I think it points to the alternator.... any ideas? (thanks J-Ri for all your input with this problem!!)

Ok, took the battery to autozone to charge and test it. Surprise, surprise, it failed! So, bought a new battery, and will now monitor it to see if the drain is still happening or if it was just the battery.

Yeah it sounds like it was the battery all along. The only question is if the alternator will keep the new one charged. It doesn't really sound like the alternator was tested.

Just for fun, I checked the AC voltage at the battery while the car was running - 32.8 volts AC on the display with the meter set to 200 VAC! Something about this doesn't seem right, and I think it points to the alternator.... any ideas? (thanks J-Ri for all your input with this problem!!)

I'm not sure but I think if you measure AC voltage between the battery terminals you'll normally get a reading like that. But if you measure AC voltage in series with say the pos battery terminal there should be very little AC voltage (the only safe way to do that with a voltmeter that I know of is to unhook the alternator positive wire and test in series there, or maybe between the positive terminal and pos cable while connected ). If you had high AC voltage from the alternator output measured in series that would indicate bad diodes in the alternator. Maybe not but that's how I understand it.

You shouldn't have any AC voltage across the battery terminals. It's acceptable to have a few millivolts AC leakage out of the alternator, but should never be even close to what yours is. Your alternator is junk, the rectifier is bad allowing AC voltage out. The alternator produces AC current which is then converted to DC inside the alternator. Check out http://en.wikipedia.org/wiki/Bridge_rectifier for a full explanation of that. Don't run the engine any more until you replace the alternator, as it could damage the new battery. Basically, the alternator is charging and discharging the battery thousands of times per minute, and at a much higher voltage (almost 3x) than the battery is designed for.

Yeah I definitely agree there should be only a few millivolts of AC votage at the alternator +B. I think I gave incorrect info about there being any AC voltage above a few millivolts across the battery. There shouldn't be across the battery either. There's little clear info out there about AC voltage in the charging system and some sources claiming as long as it's under 30V that's normal and I think that's wrong. Electrical is still my weak point. I agree with J-ri.

Your alternator is probably bad due to faulty diode(s) in the rectifier (very common problem) and is why you were having battery propblems. That's why I suggested you have it load tested and asked if you had somewhere between 13.6 and 14.8V with the new battery (even then it could still drop under load). You should have the alternator tested on or off the car and replace it.

Allright, another update... so I replaced the battery, and the drain continues (although not quite as fast, still loses .5-.6 volts in 3-4 hours). So, it wasn't the battery after all. Amp draw remains .08 amps when the car is off (I checked across the console fuse, and ALL of the amperage is running through there).

Today, I took the alternator (thinking it might be a diode) to Autozone. They put it in their machine, and it passed with flying colors. While removing the alt, I checked amperage in line with the positive connection, and it was 0. So, it wasn't the alternator diodes.

Here's the weird thing: After reinstalling the alternator, I fired up the car for about 10 seconds and shut it off again. I went to check the belt, and heard a very faint high-pitched whine coming from the alternator - I've never heard this before, but I never got that close to the alternator before either (almost touching it with my ear). Confused, I checked the voltage at the battery and it had lost .3 volts in just a few minutes (could have been from starting the car). I checked voltage between the battery positive and the alternator positive - .01 volts. I checked amperage, and came up with .01 amps. This whole time, the whine was still there. Finally, I disconnected the battery and the whine stopped - the voltage and amperage between the battery positive and the alt positive had stopped as well.

I reconnected the battery, and there was still no whine. Checked the battery voltage, and it had gone back up .2 volts. I restarted the car, ran it for a few minutes, and shut it back off. The whine was back again! This time, instead of disconnecting the battery, I disconnected the plug on top of the alternator (I think the sensor?) and the whine stopped again. I reconnected the plug, and no whine. I restarted the car, ran it again for a few minutes (turned a few accessories on and off, checked the charging voltage of the alternator (14.5), then shut the car off. This time, the whine did NOT come back. Nor did the volt and amperage running from the battery to the alternator.

So what the heck is going on here? Besides this new thing (the noise the alternator is making), the only other thing I think of is that the computer is turning something on every few hours, and I have no way of testing that. Nor can I test the actual drain on the battery when the alternator is making that noise, because disconnecting the battery to test is stops the noise! Aaaaaarg. Thanks for listening everyone!

The battery voltage dropping .5-.6V in several hours may be normal. What's the voltage at after it drops?

If you had 30-some volts of AC voltage across the battery terminals, the alternator is bad. It should not allow more than a few millivolts of AC voltage. Double check that your meter wasn't on auto-range and reading mV.

The whine from the alternator is not normal, and also suggests a bad alternator.

The connector you disconnected from the alternator is the "no charge" indicator and the "GEN-L" wire. The no charge wire provides a ground to the no charge indicator light when the alternator is not charging. The GEN-L terminal is an input to the alternator that controls the duty cycle (% on-time) of the field coil. That is how the output from the alternator is controlled. Remove this connector and check the amperage on that fuse again. On some models, the alternator is controlled by the instrument panel module.

If you want the check the parasitic draw without disconnecting the battery, get a clamp-on inductive ammeter. I've got one that was a couple hundred $, but sears has one that looks good for around $70. They're not quite as accurate as the probe kind, but are much more convenient and work just fine for finding parasitic draw. I still don't think you're draw is too high. .05A is good. Like I said before, .08A for 100 hours is only 8 amp-hours, which is nothing on a 60 amp-hour battery. It's leaving you with approximately an 87% charged battery after it sits for 4 days.

EDIT: I went to the Exide web site to see if I could find the amp-hour rating for a 75 series battery. I couldn't, but the reserve capacity@25 amps is 90 minutes, which is 37.5 amp-hours. And that's to where it will still pass a load test. http://www.exide.com/products/automotive/exide_60_specs.html That's their lowest quality battery, and Exides are certainly not the best brand, so chances are you got a better one (Guessing Duralast since you had it tested at AutoZone)

As an example of the voltage drop in 4 hours, on Friday the battery voltage went from 12.7 to 12.25 in just over 4 hours. It still started just fine at that point, which is definitely more than the old battery could pull off!

The instruction manual for my multimeter doesn't mention autoranging, so to test that idea I checked AC volts on my other car (2005 Matrix) and got the exact same reading (30-32). That car has no problems with battery holding charge, so you are probably right about the auto ranging (or I am doing something wrong with that measurement).

I turned the ignition in the cavalier to "on" without starting it, and the alternator makes that same noise in that situation, and shows voltage from both wires going into the alternator harness. When I took the key out, the noise stopped. Besides those first two times, I can't make it happen anymore (maybe I had the plug a little loose). So now I am letting the car sit overnight again to see if there is still a draw, or if I somehow magically "fixed" it by monkeying around with the alternator.

The instruction manual for my multimeter doesn't mention autoranging, so to test that idea I checked AC volts on my other car (2005 Matrix) and got the exact same reading (30-32). That car has no problems with battery holding charge, so you are probably right about the auto ranging (or I am doing something wrong with that measurement)

Well, to begin with, a computer controlled car should not run at all with that much AC voltage because it would screw up the computers inputs and outputs so badly. So, I bet it's something in the meter, mine never reads over a few mV on a good alternator.

There's also a possibility your meter is wrong. What brand is it? If we're talking about fixing an error of .03A, I would ignore it unless you're using a Fluke or another high quality meter. Also, you can check the accuracy of the voltage by checking a new AA battery. Should be very close to 1.6V out of the box

Allright, another update... so I replaced the battery, and the drain continues (although not quite as fast, still loses .5-.6 volts in 3-4 hours). So, it wasn't the battery after all. Amp draw remains .08 amps when the car is off (I checked across the console fuse, and ALL of the amperage is running through there).

It might not have been the old battery causing the drain before but the battery was probably ruined. If you are losing .5-.6 V then your battery is discharging. You are not showing a parasitic drain so you add that to the AC voltage you found and the alternator whine and it all adds up to a bad alternator.


Today, I took the alternator (thinking it might be a diode) to Autozone. They put it in their machine, and it passed with flying colors. While removing the alt, I checked amperage in line with the positive connection, and it was 0. So, it wasn't the alternator diodes.


The thing is if all they do is test the voltage output it may not show the problem. The amperage has to be checked under load. there is a possibility they didn't check your alternator right. There's also a possibility you have a problem in the circuit at the PCM connecter at the alternator, but very doubtful if no check engine codes for are being set.



Here's the weird thing: After reinstalling the alternator, I fired up the car for about 10 seconds and shut it off again. I went to check the belt, and heard a very faint high-pitched whine coming from the alternator - I've never heard this before, but I never got that close to the alternator before either (almost touching it with my ear). Confused, I checked the voltage at the battery and it had lost .3 volts in just a few minutes (could have been from starting the car). I checked voltage between the battery positive and the alternator positive - .01 volts. I checked amperage, and came up with .01 amps. This whole time, the whine was still there. Finally, I disconnected the battery and the whine stopped - the voltage and amperage between the battery positive and the alt positive had stopped as well.


OK there's bearing whine (more like sqeak) and there's alternator whine which usually indicates bad diodes. Sounds like diodes. If you measure across the BATT terminal with it hooked up like that, you're not going to see any volts or current. You need to put the multimeter's pos terminal on the alternator BATT and the meter's negative terminal to ground.Also it's not a good idea to unhook the battery with the key on ON or engine running.



I reconnected the battery, and there was still no whine. Checked the battery voltage, and it had gone back up .2 volts. I restarted the car, ran it for a few minutes, and shut it back off. The whine was back again! This time, instead of disconnecting the battery, I disconnected the plug on top of the alternator (I think the sensor?) and the whine stopped again. I reconnected the plug, and no whine. I restarted the car, ran it again for a few minutes (turned a few accessories on and off, checked the charging voltage of the alternator (14.5), then shut the car off. This time, the whine did NOT come back. Nor did the volt and amperage running from the battery to the alternator.


It's not a good idea to unhook the connecter at the alternator with key ON or engine running either. When you got 14.5 V at the battery that indicates your alternator was charging the battery at that time. You might have an intermintent problem.

So what the heck is going on here? Besides this new thing (the noise the alternator is making), the only other thing I think of is that the computer is turning something on every few hours, and I have no way of testing that. Nor can I test the actual drain on the battery when the alternator is making that noise, because disconnecting the battery to test is stops the noise! Aaaaaarg. Thanks for listening everyone!

You don't really need to unhook the Battery. Just measure voltage across the battery terminals and see if it's in the 14V range. You can also check that you have +battery voltage between the Alternator + output and -battery terminal with key ON. You can inspect the connections and wires at from the alternator.

I think you should take it to a different autozone or advance and see if they can test your alternator on the car properly. I still think you have a bad alternator.

It's not a good idea to unhook the connecter at the alternator with key ON or engine running either.

Reread what he originally typed, I take it to mean that it was making the noise with the engine off, which would certainly indicate a problem with the electrical part of the alternator. OP, can you clarify whether the noise was with the engine running or with the engine off?

Sorry if I was unclear about that noise - it was definitely present with the engine OFF; don't worry, I would never disconnect anything with the car running (its broke enough as it is!). To make it a little more clear, it is a very high-pitched whine, but it is EXTREMELY quiet. I had to have my ear about 3 inches from the alternator to hear it.

The noise comes on when I turn the ignition key to "on" without actually starting the car. Occasionally, it stops when I take the key out, but it sometimes does not stop until I disconnect the battery or disconnect the wiring harness on the alternator. My guess at this point is that it is a noise related to the field generator - unfortunately, I think this means the PCM is leaving the field generator on when the car is turned off (sometimes). Like I said before, I don't have a way of testing this because, convienently, disconnecting the battery or removing the fuse stops the problem - then the draw reverts back to .08 amps (of course, this is just a theory at this point).

Finally, I noticed the other day, and again today, that the black plastic part of the alternator (it has little vents on it, and is where the harness plugs in) wafts warm air when the engine is cold. The alternator itself is NOT warm to the touch - and I wouldn't say the black plastic part is "warm," its more like a slightly warm draft rises up out of it. At autozone, they told me that this is normal if there is a big drain somewhere else in the system, as all the power from the battery runs through the alternator on its way to the rest of the car. I don't really agree with that, and I think this is an important clue to the problem.

Let me know if this clears up my current situation!

I was just cautioning not to unplug the battery and the alternator connector with key ON or in RUN, not saying you have that's all. I would forget about the PCM connectors to the alternator. You don't have any trouble codes related to this circuit, and the way to test it is with a scanner and backprobing the connector with a voltmeter, and the battery doesn't need to be unhooked anyway. I doubt your problem is there. The field and rectifier are always "on" because it's hot at all times from the battery. You have some noise in the alternator with key off. Why not just simplifying things and have the alternator properly load tested on the car at one of the parts store. I'd be surprised if it passed, unless it was an intermitent problem.

This is probably the final post until this problem starts happening again (if?). Since I installed the new battery, the car has not been dead in the morning - although I unplugged the battery at night for the first few days. The voltage is always lower in the morning by .3 or .4 volts, so if the drain is still happening the battery is taking it well. I will let it sit this weekend without driving it to see if the drain will take the battery out after 24-36 hours (it hasn't sat for any longer than 12 in the past week). If it does, it will be going to the shop as I have simply run out of ideas (not to mention patience). If that happens, I will post the results! Thanks to everyone for helping me out, you've probably saved me a lot of money!