GMT-800 5.3 alternator recommendations?

[Martinjmpr]

Coming home from a camping trip this morning - everything was working fine all weekend, then driving through slow traffic in Fort Collins, I noticed the battery light flashing and the DIC was intermittently displaying a "battery not charging" message. I looked at the dash volt meter and it was showing right at 12v (where normally it's at 14 when driving.) I switched the Scangauge to show volts and it, too showed 11.9 - 12v.
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Took almost two hours to get home and I watched the SG as the voltage dropped the more I drove. I was hoping the 2nd battery would be able to supply enough voltage to keep me going until I got home since I had the wife, the dog, two kayaks on the roof and was pulling the trailer.
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By the time I made it home, voltage on the scangauge was showing as 11.3. Parked the trailer, put the truck in a spot where I knew it could stay for a while and shut it off.
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Took us a few hours to unload and rest and I just went outside to check it. Starter battery is showing 11.8v, house battery is showing 11.86v. No loose connections on any of the battery terminals and the serpentine belt is tight as well- I'm assuming this means it must have been the alternator - what else could it be?
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I was just going to pull the alternator off this afternoon and take it to my local O'Reilly or NAPA, any reason I shouldn't? (I want to pull the old one because I know they can test it, also I figure they'll hit me with a core charge if I don't have one to turn in.)
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According to my RPO codes, my 'Burb has the 145a alternator. Any recommendations for a replacement? Any particular brands to avoid? Is there a high output option?

 

[Ducky's Dad]

My story is old, but similar. Had an aftermarket hi-output alternator in my '98 Z71 with dual Optimas. Alternator failed in the desert and I got almost 100 miles back to civilization on batteries alone, then the truck quit just as I got into the first town. Had to call for a tow the last couple of miles to a GM dealer. Sunday afternoon, middle of nowhere, next day all they could get their hands on was a GM 105 amp alternator. Good news is that it came with a lifetime warranty as a GM part installed by a GM dealer, and it's been in there for 15 years with no problems. Not hi-output, but it works and it's paid for and guaranteed for as long as I have the truck. Bad news is that the failure fried both Optimas and the truck's factory security module, and the batteries' outgassing took the paint off the inner fenders and hood. Sounds like yours is not as severe, but I'd think about a dealer-installed alt if planning to keep the truck forever.

 

[Martinjmpr]

Dealers were closed so I got a new one at Auto Zone with a lifetime warranty. Bit of a PITA to get it back in (the "horns" for the bolts were just a smidge too small - a BFH helped get the alternator into place.)
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Much to my surprise even at ~ 11.8 volts my battery was able to start the truck (maybe it sucked a little power from the 2nd battery?) Either way I've got the starter battery on the charger now. Once that's topped off I'll charge the house battery for a bit and then call it good.
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For our next camping trip it is 240 miles to our campsite, one way, and most of that will be interstate (I-70) so I'm thinking that will give me plenty of opportunity to "top off" both batteries while driving.
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It was $170 I didn't plan on spending but all things considered I guess as mechanical problems go, that was a relatively benign one. :sombrero:

 

[Stryder106]

My alternator is original 105a and is now 15 years old. Never had any issues with it, but was considering getting a high output one. Now I'm starting to rethink that...............................

 

[rayra]

105, 130, 145 are the options, so you were already at the top for factory versions. Lots of higher output versions available in the car audio and emergency vehicle markets, for a lot of money. The emergency vehicle versions are also configured to deliver higher output at idle, which could be useful in the 'ExPo' sphere.

The internal voltage regulator / rebuild kit costs about a third of what you paid. And it's really easy to do the work. I did it a few years ago on our Tahoe. I should probably add those pictures to the 'Hey Vortec Guys' topic.

 

[Burb One]

I ended up with two alternators
However, ya i just went with one Autozone and one O'Reilly 145 alternator. figured, wherever I am in the country, I can get a roadside lifetime replacement. lol. The big dollar ones are not worth it IMO.

 

[Martinjmpr]

105, 130, 145 are the options, so you were already at the top for factory versions. Lots of higher output versions available in the car audio and emergency vehicle markets, for a lot of money. The emergency vehicle versions are also configured to deliver higher output at idle, which could be useful in the 'ExPo' sphere.

The internal voltage regulator / rebuild kit costs about a third of what you paid. And it's really easy to do the work. I did it a few years ago on our Tahoe. I should probably add those pictures to the 'Hey Vortec Guys' topic.

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I'm guessing that's above my skill level. Hell just changing the alternator was enough of a chore for me.
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Out of curiosity, what usually fails on alternators? This gave absolutely no warning. One minute I was driving along, then all of a sudden the red battery light started flashing with the "battery not charging" message coming up on the DIC.
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I charged the starter battery last night for a couple of hours, it read 12.76 when I disconnected the charger. Will probably drive the truck a bit today to see how much that charges up the house battery before I decide whether I need to charge the house battery (which is a Marine/RV Deep Cycle.)

 

[RedF]

I believe that a 160 amp alternator is also fairly common.

 

[pawleyk]

I believe that a 160 amp alternator is also fairly common.

I managed to score one of these off Rock Auto. It's a DELPHI brand, 4-pin alternator. Not sure what they put it in, maybe the Hummers and other luxury 6.0L powered rigs?

 

[Stryder106]

A question: When going to a higher output alternator do y9ou have to change the serpentine belt to a different one? I haven't found an alternate part number for my belt, so I'm curious if they are better internals or if they are spinning them faster with a smaller pulley.

 

[pawleyk]

I remembered changing belts, so I just measured the pulleys on both my old 105amp and my new 160amp alt. The pully on the old 105 is 2-3/8" and the 160 is a solid 2.5". Looks like they actually slowed it down a bit.

I also lied when I said the 160 was a Delphi, turns out its a Bosch AL8787X.

I'd throw pics on, but I can't figure out how to do it from my phone.

 

[Buddha.]

Dealers were closed so I got a new one at Auto Zone with a lifetime warranty. Bit of a PITA to get it back in (the "horns" for the bolts were just a smidge too small - a BFH helped get the alternator into place.)

I had this trouble once, gave it a tap and snap, the ear broke right off. A simple alt swap turned into a trip to the junkyard and another $40.

 

[rayra]

better to take a flat bastard file to the inner side of the ears or the horns, than ********** it with a hammer. As you found out. with steel parts you can get away with a hammer. Aluminum, no.


As to what fails, there's only a couple parts.

The generator armature; the rotating core and the wire windings in the outer case. Sometimes you'll get a fracture in the outer windings, typically that's a thermal shock sort of thing, ice cold water on a hot alternator.

The springloaded contacts that contact on the rotating shaft, the 'pickup'. IIRC those are carbide and they do wear down / out. They're also easy to replace and the there's a trick with a toothpick / nail when doing so that GM alternators are designed to accommodate, with a small hole in the back casing. The two contacts are in their own plastic housing.

The internal voltage regulator. That's a solid state part (mostly) and almost always the point of failure.

There's a couple other parts in older alternators / generators, any model-specific rebuild kit will have what you need. In the case of the GM alternators you can get specific parts only.

The rebuild process is easy. Disconnect and dismount the alternator. make a reference mark across both front and rear halves of the casing, as it can go back together in 4 different positions. There's four long screws around the perimeter that hold the two halves together. The two halves should come apart easily, but might take some (gentle!) prying. When you pull the front half off - which takes the center shaft with it - the springloaded contacts will come out of their casing. Don't worry about it, that's wha tthe toothpick is for on reassembly.
Then there's a couple screws holding each of the parts in the casing. Pay attention how the parts fit and overlap before you take it apart.
With everything apart give it a good cleaning and you want to make sure any solvents are gone before you energize it again.

some regulators have a little sight window in their body, similar to that in the HEI distributor ignition control module in older vehicles, if the thing is blown / cooked, it vomits some colored goo behind the window. Same sort of principal as the old sight window in SLA batteries.

Reassembly. The contacts housing as a thru-hole in it and so do the contacts themselves. You get the contacts back on their springs and shoved back in the housing, one at a time and use a toothpick thru the aligned holes to trap them in. The housing gets skewered like an hors-d'oeuvre. Get your new parts reinserted and stacked properly and tightened down. The toothpick should be sticking out the back of the casing. Put a SMALL bit of hi temp bearing grease in the back casing bearing cap. Slide the two halves together, might take a little jiggle to get things to seat, it should seat fully - do NOT try to draw the two halves together with the scrws if it doesn't come together, likely means you've got parts stacked wrong and you WILL break something trying ot force it together. once the perimeter screws are set just pull out the toothpick. You'll hear / feel a couple click-snaps and the contacts spring into contact with the shaft.

And that's about it. Reinstall the alternator.

It's really not difficult. Nutdriver, 8 screws, plus the alternator dismount.

One other thing I've noticed on these newer GM vehicles, the main wire from the alternator to the battery is a fusible link. I have no idea why or what that is about. Nor have I seen any anecdotal reports of this being a problem. But I've had electrical trouble on other vehicles in the distant path where a fusible link caused me some grief. So I'm thinking I need to find a spare to cart around when I'm out in the middle of nowhere. Or maybe fab up a NON-fusible piece of appropriate gauge wire, so I have a better chance of driving home if some related trouble develops in the middle of nowhere.