2001 impala battery dies every few days

big al

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#1
My daughters impala LS with the 3800 battery dies about once a week or every other week, i have installed a known and confirmed very good battery from my truck in it, same problem as her original battery. Car will start fine for days even when she will leave in the morning,then in the afternoon comes and it will need a small jump then be fine for days again. She only drives a short distance each day but always let's the warm up run for a while. What I have noticed is that the alt doesn't (turn on ) right away, after about 10 seconds it'll kick on and start charging. I know the older alternators could have this problem,charge fine while running then die overnight due to bad diodes, but I'm wondering if the newer alternators still could suffer from this type of problem?? My previous 2000 impala LS never had this slow acting alt, it was on as soon as the fired. When I get home today ill do a draw test and see what shows, im suspecting probly not see anything because its somewhat intermittant, what do you guys think about the older and newer alts having similar problems
 

billr

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#2
The basic alternators are pretty much the same. The voltage regulators have changed over the years, moving from mechanical (relay) type to solid-state and now controlled by the PCM in some cases. There have been various arrangements of the rectifying diodes and such, but that is more a manufacturer-to-manufacturer difference, not "old vs. new". I had a similar problem for years, very intermittent; not good for batteries as they sulfate. What I finally pinned it down to was the ignition switch/lock and steering wheel lock circus; the alternator "boot" circuit was being left energized as if the key was in the "run" position. Let me try to explain:

My key can be removed with the SW in any position, it may not "lock" until moved a little and the locking-pin drops into one of the many slots for it in the SW hub. Once that lock pin drops into position, then whatever there is in the lock cylinder that enables that lock-pin action also moves to its fully-seated position and the cylinder (and switch) are firmly in the "off" position. Before that SW lock-pin engages, the lock cylinder position is just a bit "iffy" and may leave the switch partly "on". This didn't start happening until about 20 years of service, and is related to wear in the lock cylinder, I expect. My solution is to simply wiggle the SW a bit to be sure it is locked and wiggle the key a bit after that to be sure it is "centered" in the "off" position before removing the key; haven't any problems after adopting that easy "fix".

Your problem may not be the same, but my experience is worth considering, as the symptoms were exactly the same!
 
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#3
A parasitic draw test sounds like a start- remember the modules need time to go to 'sleep' -

some thoughts - trunk light, glove box, , you know I blame anything aftermarket... radio, alarm, navigation,

you could put a DVOM on the alt output (big wire) - set it to AC voltage to check diodes.. then when eng OFF remove wire and put DVOM (dc now) - pos lead on wire neg lead to alt terminal... this will show an internal grnd.



As always Billr has a good tip - Bill i want to ask - when the switch does NOT "seat" itself correctly are there any other accessories that stay energized- things like- wipers, washer, blower, signals etc. If something then Big Al could check their operation is it also delayed?


PS: My boogie man remote starter?
 

billr

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Kev2, there was no obvious sign of anything else staying one (lights, radio, heater blower, etc). It took me years to track it down, as it was so intermittent and by that time I was only running the car occasionally. Sometimes the battery would hold a charge for many months, then the next time it would lose a charge just overnight. When the alt VR/field was being energized it would draw about 4A, as I recall. Obviously, this whole scenario may have been unique to my particular switch design (a '69 GM) and not applicable to the OP, but it bears keeping in mind.
 

big al

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Strange as it may sound , the first time this happened I suspected ign switch, and taught her to just as bill said . These switches in these years impala were crap, , both my impalas ign wer finicky, eau time the battery has been dead after the switch seems to be centered in the off position and she will wiggle a little as she takes the key out to make sure it locks in the off position. Kev , to answer your question- no absolutly nothing shows any indication of being powered up or left on (if the switch is acting up). But one of the reasons I asked as on a late 70s 350 i had an alt do this me,charged fine when running, would drain battery when shut off, changed alt and was normal again that why I asked if they were still the same as older ones. Also very interesting about the ign switch I had a suspect feeling about that switch the fist time it happened and checked it out, ha even removed key and everything stayed on, played with it and everything went off
 

big al

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Now I here that cars and thirds ign switches are pain to do and the car most likely won't start with out dealership reprogramming the BCM, is this true??
 
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#7
Some thoughts came to me ... and worth adding... if you move the key to off position and remove BEFORE you place shifter in P the system goes AFU. Can remove key and walk away there is still power where it should not be...

Can you did you check for B series codes?
would you need a diagram-

Do you want a wiring diagram?

PS - scan for codes 2 in question P0621 and P1637 they will NOT illuminate the MIL.
 

billr

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Thinking about it more (it was about 20 years ago that I "solved" it), I think there was a relay that was being held-in when the ignition switch wasn't properly "off". That's how I found the problem, I heard that relay clicking when I was doing something with wiring and all switched power should have been off.
 

nickb2

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#9
Ok, took time to read all post before shooting myself in the foot with a beginner comment like the vacboost on the focus.

Need to know if this has a bosch NCB1 or delphi CS on it. Difference is 105 amp and 125 amp and 300$ difference between the two. Most probably depends on options. That is where load shed levels may come into play.

PCM signal turn on, external voltage regulator to pcm hence alt mounted. Had to correct that also because I realized I said external as in mounted on firewall or something.

Thought I would also post this ace pdf. It talk about load shed levels. ;)

To know the difference between the NCB1 and the CS is as in that the bracket/spacer #4 in the second snapshot is for NCB1 bosch.

Oops, had to modify, the 1st snapshot is of the battery rundown and load management wiring.

See that field terminal connected internally to regulator and external to pcm and tsb was issued for corrosion on alt/reg side causing pcm to not wake up until resistance was overcome causing no charge when needed. Especially at cold start up. Hope this helps and made more sense than my focus comment. :D

I think the tsb was issued for the bosch model only. However a bit confused to make an error here cuz that tsb was only for the 3.8 police package/taxi and asks to replace the generator VR ground screw only.

So since you have the 3.8l, will assume you have the bosch. However, can never really rely on these alldata and old fart brain syndrom to remember all these details. Just look for that #4 spacer.
 

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nickb2

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#10
Hence my reason here is that maybe even though you have a nice new truck battery in it, and cold weather, (disclaimer, I have no idea where you live, but up here, we know cold weather starts and see this all the time) maybe that vr ground bolt is preventing a full charge on short trips and eventually bringing that battery down to a no start state and cold weather does the rest.

Once in a while, after that boost you give her, your daughter only drives it a few miles, who knows? It is as you say NOT your car. Or not anymore that is ;)

Please watch at minute mark 4:50 of this video for where the corrosion happens. https://www.youtube.com/watch?v=7PIR-lWGV6U

Also at 5:12 minute mark he states exactly what I am trying to convey by replacing that VR ground screw.

Hope this helps, tried to post this before, but BAT server crashed, so had time to mark the minutes 8)
 

nickb2

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#11
So here is me being a bit intrusive yet telling you to educate your daughter, that until this condition is not rectified(pun intended), she must start the vehicle with NO LOADS on in cold weather. Which means turning them OFF before she shut the vehicle off and go around the block to give it a surface charge for the next day. So you, as a father, don't need to run out in your long johns to boost it.

Some folks like their car nice and toasty once their first coffee morning is done cuz it is nut freezing cold and lets say, the left the defog on, or the heater fan full blast, and all this just to go get a cup of joe.

This is where the dangers of convenience outweigh that pesky remote starter. If you only have a few amps left lets say, and to unlock all door and trunk take 10 odd amp, and the blower take 20 amps to start up, your cold cranks amp just diminished in a fashionable way, and exponentially drop as freezing temps lower.

Factor in a bad field ground which prevented twenty minutes of run time to charge only 20% of the battery, just to let it sit for 8 hours of study or sleep, that battery is now dead, even if new.

When I say no loads, I mean no cell phone charger, no mp3/4 player/charger or any other crap and use the key to unlock the door, and yes, maybe freeze for awhile. At least she will be on her way.
 

nickb2

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#12
This is a snapshot of what I mean by a warm up cycle being of no use unless rpm is applied and restrictive "f".

Notice 20% charge rate on what GM considers normal. These v'6s rpm at what? 650-700 in cold weather? Imagine what charge rate on battery is if no excitement from vehicle operator with limited knowledge to entice the generator into action.

Read the first paragraph of the snapshot

Second snapshot is what her impala can draw in the first minutes of what most ppl consider normal accessories. Not good for a discharged battery if not driven or 24km/15mph and then left to park down the street 10 minutes later, then driven home in the same conditions 8hrs later per sey.

On a snow sleeted day at 6am in the morning, that is a whopping 124amp draw with only one heated seat in action and a 20 percent battery in traffic averaging no more than 20km's per hour cuz traffic is at a crawl.

Ok, enough. I think the op gets my drift. All this on a 125amp output generator which can't charge even if the engine oil and coolant are hot after a twenty minute startup time.
 

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