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Is my alternator going for a crap ?

Lifted07

Full Member
Joined
May 5, 2011
Messages
295
Location
Winnipeg Manitoba, Canada
OK, so my 07 AV has almost 260,000 kilometers on it so it wouldn't really be a surprise if the alternator is going.  The thing is that it does not have a low voltage reading on the gauge or my bully dog programmer all the time.  The lowest it showed so far is 11.8 volts and this is no matter the speed / RPM's.  It is almost as if the voltage regulator is kicking in and out because it will fluctuate and the voltage will go up a bit to 12.3 ish and you can hear the difference in the A/C, then after a short while the voltage will be back to normal in the 14.3 ish range and stay there.  I will also mention that a couple of weeks ago when I was recharging my A/C, the voltage was showing low on the gauge and I touched the alternator and it was quite hot, so hot in fact that I burned my finger when I touched the bolt where the wiring bolts to the alternator.  I am pretty certain it is the alternator, but could there be a possibility of there being some other issue?  Thanks in advance for your opinions / advice.
 
Sounds pretty normal to me, the 07 up act a little different and the voltage does vary.
Here is a short description of it
 

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One thing I would do is to have the battery load tested to see if it's recharging OK.
 
That is normal for your AV.  We verified this at the Nationals last week. The new voltage regulators do that.

On older ones like my 2004, it stays at 14.4V all the time.
 
Mine too normally is at 14.3 - 14.5 but only recently has started to drop, but doesn't stay low for long.  The battery is about 1.5 years old.  I'll keep an eye on it.  Thanks for your responses.
 
Another thing it might be, since the weather has been so freaking hot in the east and upper midwest it could be the AC compressor kicking in.
 
I'll definitely have to keep an eye on it.  It doesn't matter if the A/C is on or not, I thought it might have been due to the heat up here in Canada as well but tonight was quite a bit cooler and it still started off at about 13.8 and stayed there even after I shut off the A/C.  Also I'd like to mention that 99.99% of the time it is always at 14.3 and maybe that .1% of the time it is at 14 or 14.1.  It could maybe be a battery going bad due to the heat here, it did go dead on me while we were away on our 2 week winter vacation.  Perhaps I'll throw my charger on it after I get it back from the garage, due to lack of time I'm taking it in to have the driver side motor mount replaced along with possibly a bottom ball joint or 2, maybe I'll get them to check the charging system too.  I'll keep you guys posted.
 
The drop is normal I researched this years ago when I first noticed it and it surfaced again last week at nationals as Trey mentioned. him and I researched it again. the odd thing here is many people don't ever look at the voltmeter that often and don't notice the fluctuation, but watch it closely if they think there is an issue. it was about a year after I bought my 08 when I noticed it for the first time after starting audio system upgrades and did some research on it.  Mine drops down and stay down for extended periods of time, regardless of accessory operation. there are however 2 ways to force the system out of this lower voltage operative state. switching into tow mode and turning on the headlights.
Below is an except from a TSB issued regarding this condition (this was issued in 2011, but I assume it continues through the 2013 model year)
Below that is a photo of my voltmeter I specifically took to send to Trey. This was where the needle was for about 6 of the nearly 10 hour drive home on Sunday in high 90 degree heat. I had had my programmer plugged in most of the way just to monitor it more closely after the discussion regarding it on Saturday and at no time was the system outside of normal operational range. I would suspect what you are experiencing is totally normal.

"Models: 2005-2011 Cadillac Escalade Models

2005-2011 Chevrolet Avalanche, Silverado, Silverado Classic, Suburban, Tahoe

2005-2011 GMC Sierra, Sierra Classic, Yukon Models

Voltmeter Fluctuation Condition:
Some customers may comment that the voltmeter is fluctuating between 11 and 14.5 volts on their full size pickup or utility vehicle. Starting with the 2005 model year, light duty full size pickups and utilities are equipped with a new Regulated Voltage Control (RVC) system. This system reduces the targeted output of the generator to 11.8-13.1 volts when in  "Economy Mode" to improve fuel economy and prolong charging system performance and longevity. The generator may exit "Economy Mode" if additional voltage is required. This will cause the voltmeter to fluctuate between 11.8 and 14.5 volts as opposed to non-regulated systems that usually maintain a more consistent reading of 14-14.4 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted.

Camper/Trailer Battery Charging Concerns:
Some customers may comment that when towing or hauling a camper/trailer, the auxiliary battery for the camper/trailer will not stay charged. In most cases, this concern is blamed on the new RVC system. While the RVC system does reduce the generator's targeted output voltage to 11.8-13.1 volts when in "Economy Mode", this feature is bypassed if the tow/haul feature is enabled. With the tow/haul feature enabled, the RVC system will stay in "Charge Mode" and the targeted generator output voltage will be 13.9-15.5 volts, depending on the battery state of charge and the estimated battery temperature. To keep the generator in the "Charge Mode", use either of the following two methods.

? The first method is to use the tow/haul mode when towing or hauling a camper or trailer.

? The second method is to turn on the headlights, which will increase the generator's targeted output voltage to 13.9-14.5 volts."


 

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Very glad to see this question answered correctly.  About 5 years ago i had my alternator replaced and again saw the same issue.  Took it back to the shop where they checked it and replaced the alternator again for no charge (apparently they didn't have this information at the time).

Since that time I often see exactly what was shown in the picture but the battery is always charged so I though it might be a computer glitch in the gauge. Apparently this is normal and makes sense that it would go into a 'maintain' mode when fully charged.  Thanks for the report..
 
I really appreciate every ones answers and feedback.  As described above about how the charging system normally operates, then my Avy is not normal  :laugh: .  Since getting my Bully Dog GT 4or 5 years ago the top gauge readout is my speed and the one below that is RPM, then battery, and then the coolant temperature.  These displays are at most about 3/8" in depth so with a quick glance at my speed it only takes a 1/2 second more to check the other 3 outputs, and my "normal" has always been 14.3 ish and what is supposed to be normal seems off to me now.  I may be abnormal as in I keep a very close eye on all my gauges as that is what my dad taught me since I started driving at 12 years old LOL.  Perhaps my battery is now finally fully properly charged
 
    Hey Tom,  thanks for all the info, and the help last week, I really do appreciate it. 
        I will admit, I was in kind of a panic with what I was seeing on my gauge, being almost 900mi from home, and with no tools with me (that will never happen again).  However, on the flip side, I did do that alternator upgrade that I've been putting off, and, I don't know if it's related to it or not, but I'm not hearing that strange whistling noise anymore.
 
Well I've had it back from the shop for over a week now, just forgot to update you guys on what the shop said.  They said that they tested the battery and the alternators output and everything is within the normal operating range but stated that because it is not within what I have normally have seen it that it is a possibility that the alternator could maybe be on it's way out, but to not worry too much about it.  On a side note I was close as to the ball joint, it was the upper one on the passenger side not the lower, and below is a couple of pics of what was left of the drivers side motor mount.



 
I'd like to share my discovery as it is very relevant here:

I have an '03 with close to 150k on it.  I suspected the alternator was getting weak due to the following:

1) Voltage swings. (14v down to 12v when stopping at red lights and/or sometimes occasionally when idling)
2) RPM would also dip and the engine would stumble a bit at the same time the voltage went low
3) Bought a new battery and noticed the first few starter turnovers were way stronger than those that happened in the following few months after its purchase
4) RPM and voltage would dip when compressor turning on.  I was almost certain this was due to my aftermarket compressor-- but read on:

I put in the new alternator and ALL of these problems disappeared!  :D

I might add that I saw *none* of the typical problems that are supposed to happen when you have a bad alternator (i.e. dimming and/or flickering headlights, needing to constantly jump start the car)

My point is that, I'm not so sure that these voltage swings should be ignored (at least on 1rst generation avalanches).  My voltage is now pretty much ROCK SOLID at 14v when running.  Occasionally the needle will move down maybe 0.5V which is barely noticeable.  It was moving down way more than that with the failing alternator.  Again, I'm not sure on '07 and above, but don't ignore this if you have an older model.

 
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