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2004 chevy trailblazer_ls
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Discussion Starter · #1 ·
Ok i have some type of electrical problem, and need some help.

About 2 months ago my battery died. I thought that was odd but didn't pay any attention to it, and has been fine since. Then this monday my battery was dead again.

So here is the problem. I think it is the alternator. When i'm driving down the road my scangauge says my volts are at 13.8, and today after rolling both front windows up at the same time it dropped down to 13.4. I just got it checked today at the dealership(free), and they say everything is fine with the charging system. But if everything is working right shouldn't it be at 14.4 volts?

But they did say there was a 1/4 amp draw when it is off. Could that part of the dead battery problem too?
 

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I believe the computer can control the alternators output- by not requiring the alternator to be pumping out electricity-- the engine can have 1 less load on it.
when the car needs more juice-- the computer can command more output from the alternator.

I would look into that 1/4 amp draw 1st.

its possible a module in your car is not going to sleep after sitting for a while.
 

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2003 gmc envoy_slt
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Use the Search function. There has been a problem posted with the OnStar module not going to sleep and draining batteries.
 

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Discussion Starter · #4 ·
Use the Search function. There has been a problem posted with the OnStar module not going to sleep and draining batteries.
I did search, and I don't have OnStar.

My voltage gets lower the longer i drive around. And then I charge the battery at home and it starts at 14.4, and slowly drops again. I still think it's the alternator. I have another appointment with another shop tomorrow.
 

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Those voltages are fine for normal operation in normal temperature after the battery gets topped off after being used to start the vehicle. You only see 14.4-14.6 for a few minutes.

There are a lot of modules that can sit around dozing, not sleeping, for a couple of hours after being turned off. The dealer should know this. The "inadvertent power" timer in the BCM is the longest one other than OnStar.

How long did the vehicle go without being run? 1/4 amp is not enough to drain it overnight.

If it's the original battery, it's overdue for replacement. Get it tested if you need reassurance, but it's time.
 

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2003 gmc envoy_slt
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:thx
I did search, and I don't have OnStar.

My voltage gets lower the longer i drive around. And then I charge the battery at home and it starts at 14.4, and slowly drops again. I still think it's the alternator. I have another appointment with another shop tomorrow.
I wasn't ragging on you about the Search. Did you remove the OnStar or do you just not use it? IIRC all TV's came with OnStar standard. Even if you don't use it, it can still cause a problem.
 

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:thx

I wasn't ragging on you about the Search. Did you remove the OnStar or do you just not use it? IIRC all TV's came with OnStar standard. Even if you don't use it, it can still cause a problem.
Craig has a fleet vehicle without OnStar, believe me I checked because I didnt believe him either.:x Mine's got something much more important than OnStar which I never used even in the first year of owning my TB when it was free, where it used to reside in my 02 is not my amp for my sub. Much better use of space!:D

Let us know whats up with the alternator test, unless your batter has a dead cell then you shouldnt be getting that drain. Wonder if your XM, HU, or alarm is drawing too much power...
 

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Discussion Starter · #8 ·
Well i just pulled the wires for all the after market stuff I did. I'll see if i still get the drain.

And WOOLUF1952 I wasn't snippin' back. Sorry if it seemed that way. :crazy:
 

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No they didn't. As Eric said the fleet vehicles don't have it. I've rented several over the years, and a very large percentage of them didn't have it.
i dont have onstar. And theres no Onstar box under the seat. Bought new.
mines an 03.
 

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2002 gmc envoy_slt_xl
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Having same problem

I'm having the same issue with my Envoy's battery draining enough over the period of ~3 days that the engine won't turn over. I tested the amp draw on the battery with everything shut off and started pulling fuses. I am seeing a0.26 amp draw after all the modules and lights power down. The onstar fuse was not pulling a load nor were any of the fuses inside the cab. I then started checking fuses in the block under the hood. I disconnected the light under the hood so it wouldn't be placing a load on the battery and discovered that even with the light off, and the hood down, the engine compartment light system was pulling 0.1 amps. Without this draw, I am now only pulling 0.16 amps which I believe is normal or, at least, significantly less.
Has anyone else experienced this? Why would the engine compartment light be drawing current even without the light on? Any answers would help, my wife is getting tired of having to jump her Envoy.
 

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The underhood light switch must have some conductive (salty?) crust or corrosion on it. Try washing it all off.

How long are you waiting before checking the current? The BCM has a timer running for a while to make sure the reading and sun visor lights are off after a couple of hours. The OnStar might not be running all the time, but it still wakes up for a short while every ten minutes to see if OnStar is sending it a door-unlock command. And finally, the BCM and liftgate modules are always awake enough to respond to keyfob remote entry commands if you have that option.

Anyway, 160 mA is about 3 amp-hours per day, so even a small battery of 50 A-H capacity should ride out a couple of weeks of being off.

How old is your battery?
 

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Craig has a fleet vehicle without OnStar, believe me I checked because I didnt believe him either.:x Mine's got something much more important than OnStar which I never used even in the first year of owning my TB when it was free, where it used to reside in my 02 is not my amp for my sub. Much better use of space!:D

Let us know whats up with the alternator test, unless your batter has a dead cell then you shouldnt be getting that drain. Wonder if your XM, HU, or alarm is drawing too much power...
No they didn't. As Eric said the fleet vehicles don't have it. I've rented several over the years, and a very large percentage of them didn't have it.
i dont have onstar. And theres no Onstar box under the seat. Bought new.
mines an 03.
Same here. No Onstar and no box under the seat.
Thank you gentlemen. I will sleep well tonight knowing I've learned something today.:thumbsup::D Now if I can just remember it.:duh:
 

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Discussion Starter · #15 ·
Anybody else have any idea? It's a new battery and still have all my accessories unplugged and it's still draining.
 

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What make of battery is it?

There is a high failure rate for new batteries, especially with the cheaper department store batteries with high CCA ratings. (If the CCA ratings are much higher than stock and the battery is the same size, compromises MUST have been done somewhere - usually with thinner and weaker plates.)

I have even heard of new Optimas going bad.

Get your battery load-tested, and let us know what the CCA rating is.

Good luck!
 

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Hi all,

Anyone can test his car battery cheaply and without any devices. Just disconnect the negative pole for at least 12 hours and then connect it and try starting the engine. If it starts well powerful enough, that means it's OK and there's a device in the car that fails to switch off. If you feel weekness or doesn't start, it's the battery.
 
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