Battery Drain Overnight 2001 Monte Carlo

This is an electrical problem concerning my 2001 SS High Sport Monte Carlo.During the last two weeks, the battery has been running down so that the car does not start, mostly during overnight periods.When I boost start and measure voltage across the battery terminals, readings are between 13.8 and 14.4 volts using a digital VOM.The system seems to be chargingproperly. I replaced the factory Delco battery (the battery was not bad).The problem did not recur for approximately 8 days.Out of the last 4 nights, three mornings when I tried to crank the car, it was either dead or so low it would not start.I have to put a booster on the battery and it only takes a few moments to get it to start.Once it's running, the cluster voltmeter shows battery charging at normal rate. However, lately during the first 30 seconds of run-time, the voltmeter sometimes flicks sharply down below 12 volts with the lights dimming, and some change in RPMs also.That may happen only once or twice.After that slight warm-up, the car usually starts and runs ok the remainder of the day.Does that sound like some type of“cold” short? I removed the alternator, and took it to a professional rebuild facility.Their bench tests showed perfect voltage and amperage outputs, with no indications of "opens" or "shorts.I re-installed the alternator, but the same problem is still present.Could it still be a faulty alternator?Man, this is getting aggravating!And my Monte is just 3000 miles out of warranty too. I have checked for all the typical voltage-draining problems, such as sticky switches, lamps, lights, etc.Everything seems to be all right. I also placed a digital VOM in series with the battery, and started pulling fuses in the upper and lower engine compartment panel.There is a drain between 1.5 and 2.6 amps (more or less) with the alarm system apparently causing the fluctuation. That is way too much discharge, so one can see why the battery would be low after 10-12 hours.I understand the computer and alarm system should pull only about 50 milliamps more or less.Anyway, pulling fuses did not make the drain go away, or even change from my previous readings.I didn't want to get into removing all the relays for fear of causing more problems. Monday I am taking the Monte in for diagnostics, to try and get this problem solved.Has any of you seen these symptoms in late model GM vehicles of this series?I would like to find the cause this weekend, if possible.Thanks very much for any helpful suggestions. Sincerely,BillSincerely, Bill

I actually had to do a current-draw test on a 2001 Impala not too long ago---same car as yours. If I recaly correctly, it drew something like .02 amps with the alarm off; .03 with it on. Or something like that anyway. So if you're drawing a couple of amps, something is definitely wrong. Another thing to remember is that on newer GM cars, the BCM (Body Computer Module or Body Control Module) still draws some power even after you have shut the car off. But the BCM goes to "sleep" after 20 minutes and uses less power then. So next time you make your test, if you just hook up the meter, don't touch anything in the car for at least 20 minutes, you may get a more accurate reading then. By the way, I would say that your troubleshooting methods are spot-on. 1. Test battery; replace if necessary. 2. Perform current-draw test on car's electrical system. 3. Test alternator. At least that's the order I would do it in. You did #3 before #2, but that's all right too. Who installed the alarm, you or someone else? Hopefully your installer would be willing to check out the alarm and its installation. Be sure to ask if you'll be charged a fee if it is found not to be the alarm's fault----I would never charge such a fee, but be sure to ask just to make sure. Also, have you tried removing the alarm's fuses to see if that makes a difference? I wouldn't go cutting into the alarm's wiring (leave that for the person who installed it), but I think it should be okay to remove fuses and then put them back.

I didnt see you mention that you had an alarm installed, although I assumed so. You mention an alarm, but I wasnt sure if it was a factory or not. If it is an aftermarket that smeone else installed, take it to them to figure out. If it was your own job, then sometimes a starter kill relay will drain the battery. There are many posibilities, s lrt us know more detail. If it is an aftermarket unit, then what brand and model, and where did you have it installed?J Rilla

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