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2003 chevy trailblazer_lt
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Discussion Starter · #1 ·
What could cause an alternator go bad so quickly? I have owned my tb since october and i have changed the alternator 3 times. I am going on a fourth one. I dont want to put it in until i know what can cause them to go bad so quickly.
 

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2005 chevy trailblazer_ls_ext
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What failed on the other alternators. If the bearing went, it could be the belt is too tight. Might be just the excess force on it.
How could there be excessive force on the belt when there is an automatic tensioner? Not to mention the tensioner usually loses tension as it gets older.

Where are you buying your alternators? What brand? If you get "rebuilt" ones, what you are experiencing is not too unusual.
 

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The belt for the EXT vehicle is shorter than the SWB, due to a difference in the power steering pump. Maybe some body put an EXT belt on his SWB?

But I agree it's ESSENTIAL we know why the alternators are being changed. If it's for an electrical symptom, it's entirely possible it's being misdiagnosed.
 

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Where are you buying your alternators? What brand? If you get "rebuilt" ones, what you are experiencing is not too unusual.
Two months per alternator ( even rebuilt ) is unusual IMO.
The belt for the EXT vehicle is shorter than the SWB, due to a difference in the power steering pump. Maybe some body put an EXT belt on his SWB?

But I agree it's ESSENTIAL we know why the alternators are being changed. If it's for an electrical symptom, it's entirely possible it's being misdiagnosed.
:iagree: about the belt. That was my first thought also. And more info is needed. Were the previous alternators failed for noise? Or lack of out-put? Or too much out-put? Where did you take them to be tested?
 

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I have the same issue. One rebuilt and one new alternator have reduced charging after a short while. My battery is 5 months old. Could a bad cell cause this? The ground for the engine and frame split at the frame with exposed wires, where corrosion gets in. Other than these two thoughts, I go to the PCM???
 

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Two months per alternator ( even rebuilt ) is unusual IMO.
:iagree: about the belt. That was my first thought also. And more info is needed. Were the previous alternators failed for noise? Or lack of out-put? Or too much out-put? Where did you take them to be tested?
No not unusual. It SHOULD be, but isn't.
What happens is some of the rebuilt alternator are very poor quality. They take the cores, fix what ever is wrong and ship them out. I had a vehicle in the early 90's that was going through alternators about one a month.

I finally got smart and bought a NEW one. Lasted longer than the rest of the car!

Now if you are replacing new or reman. ones that often, then I would definitely say there is a problem.
 

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Discussion Starter · #8 ·
well i bought my lt in october. in december the one that was in there went bad.I took the car to the garage and hooked it up and it wasnt charging the battery. so i replaced it then that one went bad and i had napa and advanced auto parts test that one. But this time i dont think its the alternator. I did a test where you unhook the battery while the car is running and if it shuts off then the alternator is bad. It ran for 5 minutes. So now when i drive at night the lights flash and the volt meter in the dash board goes low but during the day the volt meter is where it should be. What could the problem be?
 

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While standing on the drivers side, looking under the hood, there is a cable coming from the side of the engine that goes over to the frame, it is connected to another cable there, that goes up to the battery. On mine the cables are exposed where the intersection occurs. Look at yours, you can see that connection point through the wheel well. Can you see corrosion on/in the exposed cables?
 

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I did a test where you unhook the battery while the car is running and if it shuts off then the alternator is bad.

What could the problem be?
I highly recommend not doing that again. Very bad for sensitive and expensive electronics.
My first guess for the lights flashing would be a bad connection - cleaning the battery terminals on mine fixed the problem.

Do you know if the ignition switch has ever been replaced?
 

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Battery Voltage?

What is the battery voltage measured with a good digital multimeter after the truck has been turned off for more than 6 hours?

-- Dan Meyer :coffee
 

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Do you have a good digital voltmeter? You say the voltage goes low at night and the lights flash. What is the voltage on the battery terminals when this is happening?

Anybody who knows automotive electrical systems and has a good meter should be able to home in on this problem in ten minutes. Do you have a friend with a meter and such experience?

I'm guessing, and others have mentioned, you probably have a corroded or loose ground wire in the system, or something else that's easy to trace if you turn the headlights on during the daytime and the voltage drops the same way it does at night. It's not rocket science, but it does take a bit of experience and a healthy dose of skepticism to not trust every ring lug one sees.
 

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I did a test where you unhook the battery while the car is running and if it shuts off then the alternator is bad. It ran for 5 minutes.

ouch... this used to be done on the older cars of the past... even back then some said dont do it...
On NEW cars--- wow... with all the computers in the car--- id be very concerned about the equipment getting some damage from the electrical systems lack of a battery for 5 min.
 
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