Alternator problem? [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Alternator problem?


Axxman
02-09-2010, 06:32 PM
I have a 2003 trailblazer. When i first start it in the morning ( its cold up here in Maine) The volt meter only goes up to about 1/4 on the gauge. After its running for about 10 seconds i hear a click, then the lights get brighter and the gauge goes up past 14 (about 2 hash marks)
Do i need to replace the alternator or is it something else?
What is a normal reading? I thought it should be around 13.5-14
Thanks for the help

RedEnvoyDenali
02-09-2010, 06:43 PM
I believe I have read that the alternator doesn't run at full speed for a few seconds after start up when the engine revs are high. As soon as the revs drop a little the alternator beings to release current. Normal output is around the 13 to 14 volt range.

trailblazerdude
02-09-2010, 06:48 PM
I was thinking it was the alternator as well. It does exactly what you are describing; start it, volt meter goes to about 10 or 11, and then 30-45 seconds later it goes up to its normal operating range. I would think this would be the alternator, however, I will just wait for it to not work at all and replace it. Any other insight from anyone?

Super 88
02-09-2010, 06:57 PM
I was thinking it was the alternator as well. It does exactly what you are describing; start it, volt meter goes to about 10 or 11, and then 30-45 seconds later it goes up to its normal operating range. I would think this would be the alternator, however, I will just wait for it to not work at all and replace it. Any other insight from anyone?
We had a discussion about this a long time ago. My memory is not as good as it used to be - maybe Roadie (or someone else smarter than me) will come along and comment.

But IIRC, this is normal operation. I believe the alternator output is controlled by the PCM, and there was some reason it didn't charge full blast right away.

Axxman
02-09-2010, 07:19 PM
In my case im thinking the volt meter is reading to high. My gauge is reading 2 hash marks past 14 volts. I dont think this is normal. Or is it?

Super 88
02-09-2010, 07:25 PM
In my case im thinking the volt meter is reading to high. My gauge is reading 2 hash marks past 14 volts. I dont think this is normal. Or is it?

I would agree that 2 marks past 14 volts isn't normal. These gauges aren't known for their accuracy but most of the vehicles I've seen the gauge stays around 14 - some of the newer models drop to 12 after driving for a while.
You might want to check the actual output with a digital volt meter.

christo829
02-09-2010, 09:19 PM
The lag in charge rate at startup is normal, specifically when cold. It's a reduction in
mechanical load until the engine gets up to speed. It also more gradually ramps
up the charge rate so you're not just instantly pumping a full charge in to a very
cold battery.

The charge rate that the cold battery needs will be initially higher. The Roadie
had a good write up regarding temperature and charge rate, but I'm not finding it at
the moment. It should decrease slightly as the vehicle warms up.

If you think the charge rate is staying high, check it with a meter after the vehicle
is warm. At idle, ought to be around 14.1V or so. Don't believe the gauge. Stupid
"remote" gauges...if I believed mine I'd be charging my battery off the scale. All it's
really telling me is that I've got one of the crappy Delphi stepper motors that I now need
to replace. I'm debating getting all 6..but that's another issue.

Good Luck!

Chris

the roadie
02-09-2010, 09:25 PM
Agreed. We need to know the exact voltage at the battery terminals when it's been running for a few minutes. If it's higher than 14.1 or 14.2 at the battery, then measure at the output terminal of the alternator. Report back what they are.

How old is the battery that's in there now?

Axxman
02-10-2010, 06:32 AM
Thanks Guys, I will test it today, The battery in it now is about 1 year old.

Axxman
02-10-2010, 11:36 AM
I tested the battery while running i got a reading of 14.75. How do i test the alternator?

the roadie
02-10-2010, 11:48 AM
The battery could be disconnected while the engine's running and you should get something around 14 V. What you did was more of an alternator test. What does the battery read when the engine's not running?

14.75V, if it stays that high all the time, could be damaging the battery. That's a surprisingly high number, and might be evidence of a bad alternator voltage regulator. Recommend taking it to a shop or parts store that can run a battery and alternator diagnostic. Then they're not just looking at volts, but they should be able to do a load test to check the quality of the cells and internal connections in the battery.

Axxman
02-10-2010, 05:41 PM
Hey Roadie, I got a reading of 12.52 at the battery with the engine off, and 14.75 at the battery with the engine running, which is also what im reading on the gauge. Is the voltage regulator part of the alternator? What are your thoughts? Should i change the alternator?
Thanks

christo829
02-10-2010, 06:15 PM
As the Roadie said, best bet is to take battery and alternator to a shop
that can run load tests and check alt. output. 14.75 is high. Did you disconnect
the battery after you started the truck and then check the alternator output?
Did you check that after the vehicle was warmed up? If it was still cold,
that output might be that initial high rate we mentioned is needed to charge
a cold battery.

The battery might be reading 12.52 right after running, but might not hold that
charge. It's also possible to have a battery that shows full voltage but can't
maintain current.

There are some battery failures that can make charging systems try to
send more charge to the battery. It's also possible that a high output *from*
the alternator could have damaged the battery.

See what you get when the engine is up to operating temp. after you
disconnect the battery. That might help narrow down the likely suspects.
It still would be a good idea to get the battery and alternator tested, but
having a few of your own values already tested might keep them from
trying to pull a fast one on you.

Good Luck!

Chris

Super 88
02-10-2010, 06:54 PM
As the Roadie said, best bet is to take battery and alternator to a shop
that can run load tests and check alt. output. 14.75 is high.

Chris

14.75 Volts is not really high, though depending on who you believe, "normal" ranges from 14.1 - 14. 5. But some sources say:

"Depending on the load and ambient temperature, the voltage should increase to between 13.0 and 15.1 volts during this period. Most vehicles with good charging systems will measure between 13.8 and 14.8 volts on a warm day, depending on the battery type that the charging system was designed for. . .

If the output voltage is above 15.1 volts with the ambient temperature above freezing, if the battery's electrolyte levels are frequently low, "boiling", or if there is a "rotten egg" odor present around the battery, then the battery is being overcharged and the vehicle's charging system should be tested."
http://www.jgdarden.com/batteryfaq/carfaq5.htm#basics

This coincides with what I was taught in "automotive school" (granted many years ago).

Since the o/p is in Maine (as he stated) ". . . its cold up here . . . "
it sounds to me like the alternator is fine.
Also FWIW - my Haynes manual states that battery voltage with the engine running should be 13.5 - 14.7

christo829
02-10-2010, 07:10 PM
Well, if it stays at 14.75 at all times, that's pretty high for a constant charge rate.
That's also why it was suggested that it be tested after the vehicle is warmed
up, which helps cut down on the influence of a cold ambient temp.

Generally speaking, anything above 14.5 constant is high according to my
old shop teacher...who taught both the auto *and* electronics class. Of the
7 cars I've had so far, plus field equipment and vehicles, if it's been that high
on a *regular* rate, either the battery was demanding too much, or the alternator
was failing. 14.8 is acceptable intermittently, but if you pump that in to the
battery all the time, that battery will probably fail.

Granted, when he was teaching, vehicles were still only carbureted, but
considering how touchy our rides can be about operating voltages, it's
something to keep an eye on.

Hmm....maybe we shouldn't be telling anyone just how long ago that might be? ;)

I'm hoping it's his battery, but why not get the alt. tested as well?

Cheers-

Chris

Super 88
02-10-2010, 07:16 PM
The battery could be disconnected while the engine's running and you should get something around 14 V. What you did was more of an alternator test. What does the battery read when the engine's not running?



I thought that was a no - no on modern cars?!!!

chevy2_283
02-10-2010, 07:44 PM
My truck does the same thing in the morning, and I did a alternator test and everything was okay. So I talk to a GM tech and hes says it does that during the air pump test, bc if you dont allow it to do the air pump self-test soon as fired up, you will see the voltage gauge go down 2 times while driving, and when it drops like that is the air pump self-test

Axxman
02-11-2010, 06:41 AM
Thanks again for all your help guys. This morning i will test the battery cold before i start the truck. Then i will test it again after its warmed up to see if there is a difference. Is there any way to check the alternator without taking it out of the truck?

Double D
02-11-2010, 09:03 AM
When I was having my alternator issues, I talked with 2 different alternator shops, and they both stated that the Trailblazer voltage regulator is at 14.8,
not 14.2 that we are accustomed to seeing.

christo829
02-11-2010, 10:10 AM
When I was having my alternator issues, I talked with 2 different alternator shops, and they both stated that the Trailblazer voltage regulator is at 14.8,
not 14.2 that we are accustomed to seeing.

Looks more and more like my information is out of date...:duh:

Digging through the shop manuals and I still haven't found a
decent reference specification. I'm guessing I need more coffee... ;)

DoubleD, did they happen to say whether that was a minimum, maximum,
or average value?

Thanks!

Chris

Double D
02-11-2010, 10:39 AM
Max value. I changed out 5 alternators in less than a month. I finally found a new unit at advance auto that works perfect.

christo829
02-11-2010, 10:49 AM
Cool. Thanks! If you don't mind me asking, what's the good one charging at?

Cheers-

Chris

Axxman
02-11-2010, 12:48 PM
Well i checked my battery this am before i started the truck and i got a reading of 12.52. Then i took it for a ride and warmed it up, turned it off and checked it again and got the same reading. Then i went to the auto parts store and had the battery tested, They said it was fine. I also checked the voltage at the battery while it was running several times warm and cold and i still get the same reading of 14.75.
I called the stealership and talked to the service manager. He said my reading of 14.75 was normal and that my alternator was fine.
I would be curious to know what readings you guys are getting.
Thanks,
Jay

Super 88
02-11-2010, 02:51 PM
I would be curious to know what readings you guys are getting.
Thanks,
Jay

I just checked mine. The battery was around 12.4 before starting it (I haven't driven the vehicle in about 3 weeks). I had someone start it - a few seconds after the engine was running, it went up to 14.80 and about 30 seconds later dropped to about 14.70 The ambient temperature here is about 68 degrees.
My 05 has about 60,000 miles on it. The dash gauge was reading one line to the right of 14.

Double D
02-11-2010, 05:30 PM
I am also in the 14.7 - 14.8 range. What was happening to me, is the alternators that were operating in the 14 - 14.2 range, whenever there was a draw on the system(mainly A/C) the transmission would act up. Now that does not happen.

zeke36
05-25-2010, 09:41 AM
As always, great postings on this forum.

Double D, what kind of issues with the transmission where you having?

On my wife's 2002 envoy, I noticed transmission shifting rough between 1st and second. I would have never imagined that could be tied to alternator. But this symptom started around the same as the suspected alternator below.

This is what I am encountering:
I noticed headlights the envoy flickering about two weeks ago. I have never noticed it too much before. I also noticed now that the voltage meter on the dash fluctuates between 14 and down to around 11. It does this in kind of a sweeping motion, i.e. not rapid like I would expect an electrical meter to operate (not an expert here) but I suppose could just be the nature of the gauge. This happens whether the electrical system is loaded or not, so can not really tie it to any particular load.

I had the alternator tested at two different auto stores. They both kind of said the same thing. That the alternator is working but output is kind of low. I was under the impression that alternators either work or don't.

Anyways, I did my own voltage testing. Battery read around 12.6, and when engine was running, the voltage did read higher at around 13.3 or 13.5, don't recall. So to me that does looks like low output.

Does anyone agree that I should replace the alternator?
Or should I should look elsewhere for the problem?

Also, how do I tell what amps the alternator is currently?
I can't make out the weak stamping on the housing. I think it is 150 amps cause of x-ref the belt number. (Different belts for the 130 amp)

the roadie
05-25-2010, 10:08 AM
I also noticed now that the voltage meter on the dash fluctuates between 14 and down to around 11. It does this in kind of a sweeping motion, i.e. not rapid like I would expect an electrical meter to operate This is very abnormal, and caused by the alternator, with its build-in voltage regulator, not the gauge. You have a 150A alternator - parts stores that ask the "how many amps is your alternator?" question are using a specific wrong piece of software, because the right question to determine belt length is "are you an EXT/XL or a short wheelbase?"

I would swap the alternator.

Atlwrk
05-25-2010, 10:10 AM
To quote Super 88 from another thread: "We have discussed this quite a bit over the last 2 or 3 years. MOST data bases have it wrong - there is no 130A alternator for any of the I6 engines. The difference is whether you have the EXT or the SWB (short wheel base). I researched this extensively."

The P/S pump pulley is smaller on the EXT so it gets a shorter belt.

The volt gauge on the dash isn't a direct reading of the system voltage; it is the PCM's interpretation of the average voltage it's measuring. This keeps the needle from flicking around like you'd expect on regular voltmeter.

That being said, your altenator should definitely be putting out over 14 volts.

EDIT: Roadie beat me...

zeke36
05-25-2010, 01:16 PM
Thanks Roadie and Atlwrk!

I had picked up an used alternator yesterday. I had thought about bringing it back because I could not read the amps on that one either. So since its 150 amps, I will give it a try.

Now I just need to exchange the belt I picked up at parts store since they gave me the short one :(
and
exchange the gates idler puller as well. I don't like the way it fits with out the washer. (as shown in other posts, its suppose to work with out it, some people put it in that way and others exchange for different brand where you can still use the washer).

And the gauge not acting like an actual meter (cause its not one) make sense. thanks for the explanation.

the roadie
05-25-2010, 04:46 PM
EDIT: Roadie beat me...Ya snooze.....

:sadcry:

;)

zeke36
05-25-2010, 08:34 PM
I replaced the alternator with that used one. ($45) When engine was cold it was producing about 14.4 volts. After driving around for awhile it went down to 13.97 with an occasional 14 (unloaded) . So it is better, but probably could do better with a new one.

So for now I think we are okay :)

thanks :thx

chevy2_283
07-19-2010, 07:20 PM
Maybe TSB 06-06-03-004 will help out


Bulletin No.: 06-06-03-004

Date: April 20, 2006

INFORMATION

Subject:
Diagnostic Information to Clarify Effect of Secondary Air Injection System On Headlamp Flicker

Models:
2004-2005 Buick Rainier
2004-2005 Chevrolet TrailBlazer
2004-2005 GMC Envoy
2004 Oldsmobile Bravada

with 4.2L Engine (VIN S - RPO LL8) and Electric Air Injection Reactor System (RPO K18)

Attention: This bulletin applies to short wheelbase models only and supplements the information in Corporate Bulletin Number 05-08-42-001.

This bulletin is a supplement to Corporate Service Bulletin 05-08-42-001 to clarify the effect of the Secondary Air Injection (AIR) system.

A customer concern regarding headlamp flicker, headlamps dim slightly and/or battery voltage fluctuates may be easily mis-diagnosed. It is very important to capture as much information from the customer as possible. Please refer to Corporate Service Bulletin 05-08-42-001 for additional information. This bulletin specifically addresses the operating characteristics of the AIR system. Refer to the Secondary Air Injection System Description section of SI for further information on the AIR system.

The Powertrain Control Module (PCM) will command the AIR system ON during Closed Loop operation to perform an active test. The active test will pass or fail based on the response from the H02S 1. The active test consists of three tests run at 3-second intervals that are run during closed throttle (and other specific parameters, see SI for details) and will continue to cycle until the correct conditions are met and passed. The AIR pump motor has a steady current draw of 35-40 amps under normal operation, with a higher initial in-rush current. This current draw will reduce the available current for other components, such as headlamps, and accordingly may cause an intermittent dimming of the headlights. This can be compared to turning on a vacuum cleaner at your home with the corresponding dimming of your house lights. The condition can be duplicated using the special functions on the Tech 2(R) to command the AIR pump on and off.

zeke36
08-02-2010, 10:14 AM
Thanks,

However, I believe I read some where on this forum that the 2002 model does not have secondary air injection system. Or at least the TSB you mention shows 2004 - 2005, so I don't think this applies to me.

I did replace the altenator with a used one. It seemed to have a higher output, but still not real high. Seemed to solve the problem for a few weeks. the problem still occurs now though not as bad. I am going to try a new alternator and see what kind of output I get.

zeke36
08-06-2010, 09:50 PM
Allright!
After replacing the alternator a couple months ago with a used one, I determined that maybe I just go for a new one. The used one had okay output (see early post) but I was still having problems with the dash voltmeter fluctuating and rough shifting between 1st and 2nd happening occasionally but increasing in frequency.

So I picked a new Remy up at Advanced Auto Parts. I also picked up an idler pulley and a belt tensioner.

I also did the "Big 3" retaining original wires and used new 4 gauge wire. I don't have audio requirements, so just used 4 gauge battery cables.
I was thinking maybe my grounds were corroded, or too much resistance in existing wires.

Anyways, I did find my ground battery bolt looked like it had arched some, so not the best connection there. The ground wire from battery to chassis to engine looked good except where it connects to the chassis. It looked corroded. So as I was adding the "big 3" in parallel to same locations, I cleaned up all contact points.

Good news! :woohoo:
I had 14.5 volts at start up and 14.05 after warm up. No voltmeter fluctuations, stays right around 14.

the biggest thing is it shifts really good between 1st and 2nd, and actually all around. Seems like a new vehicle!:excited:

Never would have thought originally that shifting issues were due to low power, until I read somewhere in this forum.

This Forum Rocks. :thumbsup:

So either alternator or grounding issues is what I attribute it to. I don't care at this point which it was, just happy it seems resolved!